compositor: add some get'ters for the window model

Signed-off-by: Simon Busch <morphis@gravedo.de>
plugins: remove unneeded StatusBarServicesConnector class

Signed-off-by: Simon Busch <morphis@gravedo.de>
Merge pull request #66 from webOS-ports/morphis/work

compositor: add some get'ters for the window model