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.