clients: image: Add support for panning and zooming
clients: image: Add support for panning and zooming

Support for zooming by using ctrl + the vertical axis (scrolling upwards
zooms in) and panning by both the horizontal and vertical axis as well
as click and drag was added to demonstrate how axis should work.

Signed-off-by: Jonas Ådahl <67dcd8a17e758192e0cbb577ce1d62cc7da6cf49@gmail.com>

jonnylamb/weston,kwm81/weston,mchalupa/weston,Gnurou/weston,sir-murray/weston,Gnurou/weston,eyolfson/weston,krezovic/weston,mchalupa/weston,udoprog/weston,xorgy/weston,Fantu/compositor-spice,jonnylamb/weston,kwm81/weston,krezovic/weston,Tarnyko/weston-xdg_surface_present,Fantu/compositor-spice,giucam/weston,udoprog/weston,giucam/weston,sir-murray/weston,eyolfson/weston,Fantu/compositor-spice,xorgy/weston,Tarnyko/weston-xdg_surface_present