util: new timeout decorator

from http://stackoverflow.com/questions/2281850/timeout-function-if-it-takes-too-long-to-finish
mostly useful for test cases, but can have other usages
gui: size label position fix
gui: small tweaks to the overlays

draw selection overlay slightly more thick
use default system font for the text
gui: finaliazed ROI calculations (in units)
gui: small clean up
gui: add management of ROI of sparc via VA

not yet finished, but needs to be merged with work from Rinze...
Merge branch 'master' of vpn.delmic.com:odemis

fix conflicts on the overlay ROI

Conflicts:
	src/odemis/gui/comp/overlay.py
	src/odemis/gui/cont/tabs.py
	src/odemis/gui/dblmscopecanvas.py
util: clean up
gui: make ROA a VA

still need to update the overlay when the VA is updated