* Add initial implementation of TreeGrid
* Refactor TreeGrid and related classes
* Fix potential class cast exception in TreeGrid#getDataProvider
* Add smoke tests for TreeGrid
* Add communication constants for TreeGrid
Use shared constant values for hierarchy data serialization and deserialization
* Fix event ordering in TreeGrid, add javadocs, keyboard navigation test
* TreeGrid improvements
* Add TreeGrid.getDataProvider to StateGetDoesNotMarkDirtyTest exclude list
* Merge remote-tracking branch 'github/master' into tree-grid
* Remove getEscalator override from TreeGrid
Update ComboBox for new DataSource and communication mechanism
This simplifies the client side state machine.
This change does not modify the CSS class name v-filterselect.
Change-Id: I2f4a6e5252045cb7698d582be90693e00961b342