plugins: compositor: check for qt > 5.2.1

We didn't changed qtwayland to API version 5.2.1 when we switched to qt 5.2.1 so we have to
check a little bit more carefully to use the correct API.

Signed-off-by: Simon Busch <morphis@gravedo.de>
plugins: common: expose application id as property

Signed-off-by: Simon Busch <morphis@gravedo.de>