keyboard: Add support for a numeric layout
keyboard: Add support for a numeric layout

Add support for a numeric key layout, which is used for some numeric
content purpose types.

Signed-off-by: Jan Arne Petersen <8c3575d1e692bfe9fd3220cb3956503cdd270f15@openismus.com>

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