Make improve of caching for hierarchical data optional

Fixes #11477

If you use multiple UIs, the use of SLF4J would depend on the UI initialization order which could be pretty random. If you have multiple servlets, it's even better to init SLF4J in ServletContextListener.

Fixes #11502

Documents the possibility to use vaadin:// and theme:// in JavaScript and StyleSheet annotations.

Fixes #8675

Add DataChangeHandler removal in v7 Grid just as in v8 Grid.
Adding tests to the fix to verify, that NPE is not thrown.

Add check for the V8 TextField used in Table in compatibility mode. This makes clicking cell with the TextField select the row, preserving behaviour from V7.
Through, as it's noted also before, this is an improved workaround, not a proper solution to address the issue.

Fixes #11474

Removed link to and recommendation  for SQLContainer

If BrowserWindowOpener is used with constructor using Class<? extends UI> as parameter, it will have UI provider with generated url. This will not match UI beans in contextual storage and hence newly created UI will not be managed bean. Due this, injection to new UI instance will not happen. If you are using CDI , BrowserWindowOpener(String) constructor needs to be used.

Fix example of using grid.setStyleGenerator in one line

* Add Test file

* Remove redundant check for for Firefox

It seems that in older versions of Firefox (at least, older than 45) the KeyPress event should be used instead of KeyDownHandler. At some point (works already on 58 version, the current one is 65) the issue was resolved and starting from Firefox 65 this hook prevents from navigating in the pop-up via keyboard.
Simply removing additional logic makes navigating in both DateField and InlineDateField possible

Fixes #11465

Explicitly reset the value in case if it was cleared.
Ignore the case for selecting a suggestion.

Fixes vaadin/testbench#1122

* Fixing NPE when ItemCaptionGenerator returns null

Adding similar logic in setDataProvider(...) as used elsewhere in ComboBox.java (e.g. generateData(..) see line 314)

fixes issue #11434

This fix was already applied to com.vaadin.client.ui.VCheckBox but the committer forget to apply the same fix to the com.vaadin.v7.client.ui.VCheckBox. Some people are still temporarely using the checkbox from the compatibility package.

Fixes #11451

* Fix an NPE caused by the previous fix to Grid's frozen columns (#10653)

If the user managed to get two frozen column count changes into a single server round-trip before the component had been attached, the previous fix  #11346 lead to a null pointer exception since there was no diff state available.

This fix adds a null check before removing the frozen column count value from the diff state so that this will not happen.

Closes #10653

Clear contents of iframe clone that is in a Window so that when it's reattached to DOM we don't get 404

Navigation needs to be done also in doRefresh(..) in similar fashion as in doInit(..)

Fixes https://github.com/vaadin/framework/issues/11416

* Release-note updates

Change the word for describing icon swapping

* Update vaadin slogan in the release-note template

* Some formatting changes

* add client side integration for custom styles for checkbox.label and checkbox.input

* add server side integration for checkbox element styling

* add server side tests

* add client side test

Updated versions to latest ones as people often just copy past things. Added comment to urge people to use the versions they need. Removed version from archetype to use the latest by default.

* Improve VMenuBar click handling logic

During `updateFromUIDL` inside MenuBarConnector we empty and re-instantiate the components of MenuBar. When we are modifying the Menubar from the BlurEventListener of another component, we ,by this, remove widgets, therefore clickEvent is not fired and the action of the MenuItem is not proceed as a result. (The BlurEvent is fired before the click event in the chain of events. )

To improve the situation, we catch onMouseDown event , which is fired before BlurEvent,by assigning mouseDown flag to true. Then if no click event has yet happened, we delay the execution of update inside `updateFromUIDL` by default 500 ms. Then if click event occurs, it proceeds normally. The time can be increased/decreased using setter.

There is no delay, if we are clicking on the MenuBar as usual or no Blur listener is set.

This change allows setting descriptions

* Remove accidentally committed comment

* Don't update the state on the getDelayMs call

There are not [source, java] tags.

* Update clientsideapp-entrypoint.asciidoc

Adding missing ```[source, java]```

Some snippets codes do not render properly.

* Update README-TESTS

Add formatting for easy-reading;
Add missing configuration for running IE11 locally.

* Fixes #10814

* Add missing tests

Fixes #11374

Update screenshots due to update of search-minus and search-plus icons values

* Move onClick logic to the Connector

Move onClick event handling from 'VNativeButton' to NativeButtonConnector. Now works as for regular button.

Also, adding propagation of the `enabled` value to the state on disableOnClick being true

Fixes https://github.com/vaadin/framework/issues/11188

Setting read-only state to CheckBoxGroup should disable adding clicking effect. Missing v-readonly style is added to every CheckBox in the component, if it's set to read-only.

Fixes: https://github.com/vaadin/framework/issues/11113

* Add file missed from initial commit

* Verifying that option is enabled

Some of the options might be disabled on there own. Verify that option is not disabled, before removing disabled styles.

* Add missing test file