Add throttle to scroll event
Add dutch translation for aggregation
Fix #1691 (grid): generate column defs even if rowHeader already present

The data watch only generated column defs if there were no columns.  But
if the selection feature was enabled then there would be a rowHeader column
in place, and therefore it wouldn't generate column defs.
Merge pull request #1695 from PaulL1/1691_no_column_defs

Fix #1691 (grid): generate column defs even if rowHeader already present
Merge pull request #1675 from Manduro/dutch-aggregation-translation

Add dutch translation for aggregation
Merge pull request #1651 from Robinson7D/scroll_throttle

Add throttle to scroll event
fix(Pinning): Fix pinning when col has dyanmic width

Change column's width to it's drawnWidth when it becomes pinned.

Fixes #1634
fix(Column Resizing): Don't update widths in colDef

column.drawnWidth wasn't being updated after column resizing. This change
does two things:

1. Prevent updating column.width in `updateColumnDef` if it already has a
value set and the value is a number. If the column has a width that's a
number then we're assuming the user has said "I want it to be this wide"
and we shouldn't override that.
2. In the column resizer feature, update column.width, not colDef.width.
merging