Minor documentation fixes.

Fixes texts and a couple errors in IDEA, components and layout chapters.

Part of vaadin/framework8-issues#538

The SplitPanel chapter still uses a Tree in its example.

* Documentation/application screenshots update

* Avoid redundant autoboxing in BackEndDataProvider's size callback (#8127)

* Update general Component documentation

Part of vaadin/framework8-issues#538

* Documentation/application screenshots update

* Notification types fixed

* Merge branch 'documentation-screenshots-part1' of https://github.com/vaadin/framework into documentation-screenshots-part1

Part of vaadin/framework8-issues#538

Fixes vaadin/framework8-issues#580

* Update documentation chapters 1 - 5.3

Images and diagrams have not been updated,
but unnecessary images have been removed.

* Sync application declarative and architecture sections source code.

Screenshot image is updated to match the source code.

* Old datamodel image is removed.

* Ivy install image is removed.

* Remove unnecessary linking / reference

* Improved English in line 17

Changed 

"There is only one Binder instance per form and it is used for all fields in that form" into
"There is only one Binder instance for each form and it is used for all fields in that form"

Added warning where not updated.
Removed outdated documentation.
Tried to fix parts where it was feasible.

Add initial selection model documentation to datamodel-selection.

* Update portal sections (outdated message).

* Fix application documentation for 8

Updated where only small changes, mention not updated when more changes.

* Remove jpacontainer section from the docs.

* Remove sqlcontainer section.

* Add a note about outdated theme doc files.

* Update overview and field sections in the documentation

* Fix formatting

* Fix References

* Remove "chapter" word

* Fix broken docs in advanded-shortcuts

* Remove Google App Engine from documentation

Mention removal in release notes.

Part of #8033

* Update DataProvider documentation for beta

* Update Binder documentation for beta

Change-Id: I8dcf5b7576a64b26419136ca6b8927f4c2731d60

Change-Id: I5fa99627a1c3302dd905d78149e5f32c7315a5c7

Original pull request is https://github.com/vaadin/vaadin/pull/68.

Change-Id: If6dd0490a52cab3fc0bf59224546e0d295fe666c

Change-Id: I6babcadc72f3f37feff98088eee23b153a080f11

save -> writeBean, saveIfValid -> writeBeanIfValid,
load -> readBean, bind -> setBean, unbind -> removeBean.

Now setBean accepts null to reset the bean instead of throwing NPE.

Closes vaadin/framework8-issues#91

Change-Id: I42cbad5856cac11a03bfcefd0fa91a02c41b7234

Change-Id: Ib02f6c2ddc32d70f45180a03832b3dec790ecc3d

Change-Id: I94d82a6200197a6d9f6b31d66153a140333b5b1e

Change-Id: Ie90e91f61a5795c90de3c690c3b6af80ec1448d9

Change-Id: I33a4a4f0f3437a8d1733031a131afbe844c12afb

This will not be implemented for 8.0

Change-Id: Ida33b3de74c7a14def66fac6f0363a12105d8087

Change-Id: Ic40b70e692e686d638e163a224816aabeb6de100

Mostly based on comments on a previous patch that was merged.

Change-Id: I146995853b3318d89061f1d06ab4bbd859168661

BinderStatusHandler is now triggered only once per validation.
Unified ValidationError and BinderResult into BinderValidationStatus.
Renamed ValidationStatusChangeEvent into ValidationStatus.
Unified handler names for validation status.

Next patch will fix resetting of field errors on reset.

Change-Id: I9536d554d781fe599fbd7e5bcb5a9ffebe675ca0

This feature doesn't make a whole lot of sense until
form level status changes are available.

Change-Id: Ie634c4a6b3511b7cbf9e367192034934b0e0d4b0

Change-Id: I84621b6b568095b1b7f86068fa992dd570f8a103

An item level validator is run on the item (bean) after field validators
have passed. A failed item level validator will block save operations,
just like field level validators.

Change-Id: I3b918b33371ceef07cdfbd0a8b6d477d4ac26b85

Fixed broken comment on 'Calling Javascript' -paragraph.

Change-Id: I5098f21006f00eab48ce5cd55e3bb14bee040fbf

Change-Id: Ic46254b77d1226c2a00ed1ad2b2f96a452a4609a

Change-Id: Ibc5844aa4ffba5691a6e3a2d1b962ce28e2aebcf

Change-Id: Ifddcdda98090c5e5262d000a131c53109ce2c5c5

Change-Id: Id9333bae30c7bf5c24dcd0aca1cbee671c28910e

Change-Id: I1ef5a89a7e9f700a9302ff535d7e30b692316e22

Change-Id: Iecd8bd88d94b98829dfaec43b8635b1e93df330f