Add focus region bindings 'rg_<n>'

Add focus region bindings 'rg_<n>'
Default is M-Keypad_<1-9>

Add move window to region bindings 'mvrg_<n>'
Default is M-S-Keypad_<1-9>

Add invisible input window to each region for handling region focus.

On unfocused regions, set the bar border color to color_unfocus.

Add function to handle MotionNotify events on region input windows.

Fix default focus on (re)start.

Fix region-related function and macro naming.
Names referred to 'screen' instead of 'region'

Rename screen_* bindings to rg_*.
screen_* is now an alias for rg_*; old config files will still work.

Fix screen/region wording in manpage.

Sort setkeybinding calls in setup_keys.

Cleanup redundant calls when setting up the bar.