added "expo"(spaces) style mode, with commandline option eg skippy-xd -ad

added "expo"(spaces) style mode, with commandline option eg skippy-xd -ad
refactored some layout code to seperate X11 stuff from layout calc
added some vec maths helpers, 

the 'expo' style mode is different to others that its rescaled to only show the acoverlap tually used area. 
if you have 2x2 used out of 3x3.. it only shows that much.

I want to do a bit more, what I have in mind is an option to automatically pick expo/scale based on whats actually on the current screen. (if  (windows are hidden by overlap) then 'scale' else 'expo');
also i'd like to implement a grid layout option, easier to navigate with cursors a. Independant scaling is why i've refactored the layout calc