Also update declarative writing to use true instead of "" for empty
attributes because of changed defaults in JSoup. For v7, the tests are
updated instead of touching the implementations.

This patch provides a simple fix for the majority of issues. There are still issues that should be fixes by refactoring parts of the logic in AbstractSingleSelect.

This patch does not unify the handling of empty values in the TestBench elements of various AbstractSingleSelects.

Fixes #9494

The immediate benefit of this change is that ComboBox doesn't have to do
any wrapping when a ListDataProvider is set. A secondary benefit is that
a bunch of redundant type parameters and unsafe casts can be removed.

This is one of many steps towards #8245

* Replace Listing with HasDataProvider and HasFilterableDataProvider

The type parameters of the Listing interface does in practice mean that
it isn't useful for anything. This patch replaces that interface with
separate types for components that require filterable data providers and
components that support any kind of data provider.

The setItem methods are extracted to a common interface that is also
directly implemented by AbstractListing.

* Include old value in ValueChangeEvent

* Correctly reset DataCommunicator when its DataProvider is changed

* Improve ReplaceDataProviderTest

* Remove return type from AbstractListing.readItems

Renamed corresponding test packages too.

Fixes vaadin/framework8-issues#110

Touched event listeners are:
- SelectionListener
- MultiSelectionListener
- SingleSelectionListener
- ValueChangeListener
- ItemClickListener
- BindingValidationStatusHandler
- BinderValidationStatusHandler
- StatusChangeListener

Part of vaadin/framework8-issues#264

* Add a generic selection listener to Grid & SelectionModels

Fixes some inconsistent event naming and invalid javadocs.

Fixes vaadin/framework8-issues#541

Change-Id: I60c5d9f183d1955fbbd3341e3ac9f93aae755f80

Change-Id: Id7948e2f81b6a9c593ce8b71bb3a61b578344af9

Listing has been moved from AbstractListing to each individual Component.

ComboBox is now typed to String filter.

Fixes issues with declarative read of items.

Change-Id: I6918f9f8c426dcbd81546150c2cf9ed49a02bf50

Fixes vaadin/framework8-issues#388


Change-Id: I4f8045bba51d308f4343a1f6d01b3f1ddca63e69

Change-Id: I9feaad000cb16351d281d1c0037330dfb76186ff

Change-Id: I6babcadc72f3f37feff98088eee23b153a080f11

Extracts grid single selection into separate class, which
is an extension like in V7. Using an extension makes it
possible to easily add multiselect and no-select modes back,
and support custom selection models.

Adds Grid:asSingleSelect() SingleSelect so that grid can be
used as a Select in a binder.

Removes all remaining references to SelectionModels in Listings.
Renames SingleSelectionChangeEvent to SingleSelectionEvent, because
then it is unified with selection listener and MultiSelectionEvent.

Fixes vaadin/framework8-issues#424
Fixes vaadin/framework8-issues#425

Change-Id: Ie22bef29cfd4336c3f65d4e63531c578b8dd76a3

Fixes vaadin/framework8-issues#423

Change-Id: Ifd252b8feed323708a7ae73af2b836832570d192

Client side doesn't use selection model anymore.
Fixes vaadin/framework8-issues#421

Change-Id: If3ecb1c2f3a0024df9bfdfd182eaf8cf8625ac75

Change-Id: I132f814105ce97cf625e59f78731bea778ae2cfd

Change-Id: Ib867b71cab4cf5cda89f272986930297b7a84ced

Vaadin 7 compatiblity fields still use setRequired via AbstractField (legacy).
Public setRequiredIndicator is added to AbstractField, AbstractMultiSelect and AbstractSingleSelect.
Internally it is still handled on AbstractComponent & -Connector level.
Changes the declarative syntax, required -> required-indicator-visible.

Fixes vaadin/framework8-issue#419

Change-Id: I940dc66944d27584bd78e5452aee627ee3abd03a

Change-Id: I785aa82d925cadee42cc1b17d345a8923f6dc8cc

Single select components implement HasValue<T> and mutliselect
components implements HasValue<Set<T>>.

Change-Id: Ic280a43bf021efd7425cce04e75010b6745fd698

This patch updates server side add*Listener methods to return
a registration object and deprecates their corresponding
remove*Listener methods.

Additionally this patch removes add/removeListener methods which were
deprecated in 7.0.

Change-Id: I26ac5f11882512288fbbf601c7cb2aaff653ec76

Change-Id: Iec8a81424e1cae9c3dc6c760732e0d48c4a38af2

ComboBoxState now inherits AbstractSingleSelectState, but still
effectively communicates its selection via RPC.

Change-Id: I47b6a73f275e0c4c63d70d2c2c8badc95a218157

Change-Id: I340e802e5c8e6e036b54f81ec46beeb5e1c34329

Uses RPC for client-to-server but leaves server-to-client to implementation.
SimpleSingleSelection uses shared state; lazy-loading implementations to pass
selection info along with item data.

Change-Id: I97c1dfa28eee39aef43eabbfbac56cd83fa5747c

To eventually replace SingleSelection.

Change-Id: I623dfa962bce62067a5b35dc14be26b3de333e9b