Add remote desktop caps and num lock state properties
The end result is described by the last commit:
remote-desktop/session: Add CapsLockState and NumLockState properties
Will be used by remote desktop services that want to try to affect the
end result of these. We cannot let it set these directly, as these needs
to be done using virtual key events to not cause issues in all the XKB
state tracking, so remote desktop services try to deal with this
themself if they need to.