1.  Add tablet support to the event handler - DONE.
2.  Make event handler stack handle mouse/keyboard/tablet globaly, and
    not per event handler - DONE.
3.  Integrate trail playback support into into event handler stack - DONE.
7.  Coordinate system display zoom-pan-spin aware (fade in-out, similar
    to the edit plane grid) - DONE.
10. Do not allow coincedent adjacent points in a bspline (will crash) - DONE.
15. Implement proper shared OpenGL context that would work on Mac OS X - DONE.
16. Make the grid layout widget order its children left-to-right top-to-bottom,
    according to the order of the children in its list, like a comic
    strip layout - DONE.
17. Add a hidden shared context OpenGL widget instead of sharing the
    context of the first OpenGL window - DONE (related to 15).
27. Fix the orthogonal/perspective viewing switching bug - DONE.