also, added key codes from launchpad sources.
thus, a few constants change their names.
These are the current keys:
PGFWD = next page
PGBCK = previous page
SHIFT+PGFWD = zoom in
SHIFT+PGBCK = zoom out
A = fit to page
S = fit to page width
D = fit to page height
SHIFT+A = fit to page content
SHIFT+S = fit to page content width
SHIFT+D = fit to page content height
SHIFT+FW_UP = Gamma + 0.2
SHIFT+FW_DOWN = Gamma - 0.2
