Working toward making the number of markers load dynamically.
Added a simple data.c3d file (from CMU dataset http://mocap.cs.cmu.edu/subjects/02/02_01.c3d ).
Adjusted the map files to the new data.
Updated project to be compatible with Qt5.
Removed mygraphicsscene (it wasn't doing anything anyway).
Fixed (sort of) a bug in the marker widget.

Including a small data.c3d file seems like the thing to do so that
someone can run the project out-of-the-box.  At least that's the goal.