table: implement up/down/left/right focus movement
table: implement up/down/left/right focus movement

Implement focus movement by searching for the next or previous focusable
actor in the current row or column.

pwithnall/mx,pwithnall/mx,clutter-project/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,clutter-project/mx