feat: implement debounced selection api

[hyyan]

Work in progress: Please do not merge

Motivation #69

@StephanWald
The PR re-implement the selection API to be more sophisticated and faster.
The selected rows are fetched now from the client directly in real time. previously BBj waited for row selection events from the client and managed this independently.

The PR deprecates several callbacks too, which IMHO we do not need them (please tell me if anything deprecated is being used in Prodin).

Changes:

1. Simplified BBjGridExWidgetSelectRowEvent
   1. removed field public BBjVector ChangedRows!
   2. removed field public BBjVector NewSelectedRows!
   3. removed field public BBjVector NewDeselectedRows!
   4. removed method public BBjNumber getRowCount()
      5 remvoed method public BBjNumber getDeselectedRowCount()
   5. removed method public BBjVector getNewSelectedRows()
   6. removed method public BBjVector getNewDeselectedRows()
2. Parse events in the client before sending to BBj
3. Debounce selectionChanged & doubleClick events to avoid event loss in BBj Side
4. getSelectedRows returns BBjVector of BBjGridExWidgetRow
5. getSelectedRow returns BBjGridExWidgetRow for the last selected row in the grid