Cleanup of tracking core.

Cleaned up the core tracking classes. Summary of changes:

• Removed access to ca::Framework from ca::TrackExtender, ca::TrackFitter, ca::TripletConstructor, ca::CloneMerger, ca::TrackFinder and ca::TrackFinderWindow.
• Simplified the interfaces of these classes.
• General instruction-wise cleanup of these classes (applied std functions in some places etc.). In particular, streamlining of ca::TrackFinder.
• Made debugging functions in ca::Framework static.
• Moved TrackingMode enum from CaFramework.h to CaParameters.h (needed to avoid cyclic header file dependency).
• Moved some magnetic-field dependent variables to ca::TripletConstructor (they are only used there).
• Restricted the scope of many variables, i.e. turned class-fields into local variables in many instances (e.g. fvMonitorDataThread, fvTrackFinderWindow, fTrackingMode, fvWData, fvWindowStartThread, fvWindowEndThread, fvStatNwindows, fvStatNhitsProcessed, fvHitFirstTriplet and fvHitNofTriplets).
• Eliminated the Init() functions of some classes. Moved initialization to the constructors.
• Improved distinction between class-parameters and working data. Class parameters are passed to constructor, working data is passed as arguments to function calls.

Update: Absorbed !1891 (closed).