Cleanup; get rid of crufty cur_ws and cur_region and replace with

Cleanup; get rid of crufty cur_ws and cur_region and replace with
root_to_reginon, which will always give a non-crufty result. Pass the
region to all keystroke handlers.

To allow for workspace commands in empty workspaces without full-force
focus-follows-mouse, track mouse-clicks on root windows and make them
override cur_focus in root_to_region().

Also, examples of more descriptive debug output for some handlers.