Build-system clean-up part 1

* start cleaning up include directories, the goal is no redundant
include paths
* move some collectionscanner classes to shared because whey *were*
shared
* clean up config-amarok.h.cmake, we had many unused entries
* split ScanningState out of CollectionScanner.cpp bacause it needs
to be in shared

Builds for me, let's hope it will build for you, too. :-)