[packaging] Add xkeyboard-config dependency that was forgotten

Signed-off-by: Carsten Munk <carsten.munk@gmail.com>
Fixup the windowmanager extension code

ie. don't have it in its own dir

+ fixup some errors in the string matching from when extensions where
renamed from a wl_ prefix to a qt_ prefix

Change-Id: I5707c24fa727b9e49bd267eeb23fc8e43c40354f