[BZ#638437] Add num-pad keyboard merging shortcuts
Submitted by Kai Willadsen
From Peter Tyser, regarding keyboard merging:
"Perhaps the num-pad could be used? eg 9 could move a change before the right hunk, 1 could move a change below the left hunk (in 3-pane mode), 6 could replace the hunk to the right, etc. Maybe alt+num could push the hunk, and alt+shift+num could pull a hunk?"
We probably can't support using no modifiers, but Alt/Alt-Shift sounds okay. We could actually map the whole number pad. 2/8 should be next/prev chunk; 5 could cycle between panes. Delete is already delete.