gui: Added overlay test case
gui: fixed selection manipulation bug in the overlays
pigcs: FakeBus can scan for fake controllers

Kludge: pass to scan() the class, so that FakeBus can override the behaviour of Bus

also fix small simulator bugs
Merge branch 'master' of delmic-server.local:odemis
gui: Added selection overlay dragging
gui: Amazing green stream activate button icon
pigcs: fix test cases and small bugs in simulator

test cases now can be run for both simulator and real hardware, and they all pass.

Improve the timeout handling of the read() of the simulator

scan of the simulator returns 2 fake controllers (so that all the tests can be executed)
Merge branch 'master' of vpn.delmic.com:odemis