Change default border to 0
Add macro-string operation

If the single-arg shortcut doesn't match, we now treat the result as a macro.
Starting with a full-screen sized window we do the following for each character:

u: pull the bottom of the window up, shrinking the height by 50%
d: pull the top of the window down, shrinking the height by 50%
l: pull the right of the window left, shrinking the width by 50%
r: pull the left of the window right, shrinking the width by 50%
h: reduce the width of the window by 50%, centering it in the previous 100% width
v: reduce the height of the window by 50%, centering it in the previous 100% height