[keyboard] Read all xml xkb files instead of base.lst files.
Created by: scachemaille
Fix issue 67 of manjaro bug tracker that ask to have extra keyboard layout and variant that are only defined in base.extras.xml files.
also read vendor property for keyboard model and add it in combo box for a better searching. vendor | keyboard model
it read the following xml files:
- /usr/share/X11/xkb/rules/base.xml
- /usr/share/X11/xkb/rules/base.extras.xml
- /usr/share/X11/xkb/rules/evdev.xml
- /usr/share/X11/xkb/rules/evdev.extras.xml
it check to not create any duplicate.