* Added Griddragger.

* Refactored the GridDragger to match FW style

Unit tests, Test UI and documentation to come next.

* Change DropMode to BETWEEN and add Test UIs

* Simplify GridDragger API

* Fixes and unit tests for GridDragger

Fixed issues regarding drop index calculation when sourche and target grid is the same.
When the ListDataProvider is not internally using List, always drops to the end.
Updates the old data provider instead of creating a new one to preserve filters&sorting.

* Add new drop mode ON_GRID for GridDropTarget

Also adds a way to not accept drops on rows when the user has sorted the grid.
This way the bad UX can be avoided for showing the drop indicator for the wrong place when the grid has been sorted.
This has not been made default behavior to GridDropTarget since it would change behavior compared to 8.1.
Instead if is triggerable via API in GridDropTarget.

* Refactor sorted grid drop logic to server side

* Block setDropMode calls

Blocking setDropMode set values if the grid has been sorted and drop on
sorted rows is not allowed. The value is used once the grid is not sorted
anymore or the drops are allowed on sorted rows.

Fixes #9483

When CSS transform has been applied, the drag image is missing (safari),
or gets offset (FF). Fixed by using custom drag image without transform,
and checking for transforms on parent DOM tree. Does NOT fix #9408
When there are frozen columns used, the image needs should not look weird because of the frozen column transitions.
The multiselection column is now not shown it is frozen.

Fixes #9261

Also makes sure that the drop location and target row return something sensible in drop event.
Clarifies docs on drop location.

* Make it possible for grid drop target to accept dragged data when grid is empty (#9068)
* Make return type of getDropTargetRow() optional

* Add ability to set multiple drag data generators for any drag data type
and change default to be accepted by spreadsheet applications such as Excel

* Refactor Html5 DnD client side based on API review

- Moved classes to "correct" packages.
- Removed method DragSourceExtension.clearDataTransferText()
- Remove ButtonDragSource in favor of more generic API

First step of mobile DND support.

- Add mobile html5 dnd support using polyfill
- Adds a switch for enabling mobile html5 dnd support
- Adds polyfill only when needed
- Ignore native Android Chrome drag start because doesn't work properly
(no dragend event fired)
- Add documentation on enabling mobile HTML5 DnD support
- Add mention of drag-drop-polyfill license
- Fixed issue in polyfill when not using "snapback"
- Add mention of forked polyfill

Fixes #9174

Doesn't fix #9261, drag image missing on Safari when dragging grid row because
that has position: absolute and offset.

- Always set some drag data
- Set the dropEffect on dragEnter and dragOver events on drop target
- Send the dropEffect to server on drop event with disclaimer of current support
- Remove _dragOverCriteria_ and use _dropCriteria_ for `dragenter`, `dragover` and `drop` criteria

Tested manually basic DnD and Grid DnD on Mac with Chrome, Firefox, Safari.
Safari is still missing drag image (regression).

Tested manually basic DnD and Grid Dnd on Windows IE11 and Edge.
Drop event for both is still not working properly #9174.

Fixes #8401

Fixes #8931

Fixes #8400

Fixes #8397

It is possible to customize the drag data for each row. (#8706)

Fixes #8396

Change-Id: Iba9614f9809714b2d3ac564e737f03e8f89c6f82

* Use com.vaadin.v7
* Use the same class name as in Vaadin 7
* Use a "vaadin7-" declarative prefix for Vaadin 7 components

Change-Id: I19a27f3835b18980b91a4f8f9464b2adde1a5fd5

Change-Id: Ie99e3a5af908ada42a6d0eba421241ad65c0d6b4

Change-Id: I6485dee1ebba12b180a9063ed4b530f7dc63cd77

Change-Id: I4c852b7f9928e190572876690d5bef1234494a5d

Change-Id: I32625901ca27a282253df44c6e776cf9632bacda

Calculation of the frozen column width was wrong in multiselect mode.
It did not take into account the last frozen column, but added
the select column twice.
The same problem was in AutoScroller (as the same methods were
copy-pasted there), for which reason the autoscrolling was not
scrolling till the end.
This patch fixes the calculation error and removes copy-pasted code,
reusing the same code in both places.

Change-Id: I164e2fc96688088b620ad8785c533c593723f83e

Change-Id: I47868ff8b139ffc8c3c95ee6cafa95b76be67914

Change-Id: I3b160a265fe8bd16a97f895a05dc5e3a78314e07

Change-Id: I326847fd190003af9125d1386b21d9ccfc6c36c2

Change-Id: Ifa789542441e2560a57afe372c6b94d5d9e6b7e6

Change-Id: I896a6ed911000ae7d952757964117f5d28d0c27b

Test for fix submitted in 3cba005.

Change-Id: I92ee775403cbfb315499f2bcab90c895bf734832

Change-Id: Ic77338304dc7e58e49f27dcdaf0bab2e00f5bba6

Change-Id: I419ce4581d1a8b84d4236a85a1333d23f3423b2e