Initial version of classes cache and associated supporting structures. The cache logic is run in a separate thread from the UI to ensure responsiveness.

Very much a prototype at this point.
Merge branch 'master' of https://github.com/Fluxie/MFiles-Sailfish

Conflicts:
	sailfishapplication/classcache.cpp
Cleanup from prototyping.

Signed-off-by: Juha Lepola <juha.lepola@gmail.com>