CbmQaPie class as a TPie wrapper, which prevents crashes

CbmQaPie class is a TPie wrapper, which fixes the following TPie's problems:

1. When a TPie is read from a file as a part of TCanvas, it crashes at the destructor.
2. When a TPie is created via copy constructor it crashes at the destructor.
3. An empty TPie crashes at Draw()
4. When one clicks on a TPie in the TBrowser, the TBrowser crashes.
5. TBrowser doesn't draw a TPie by a mouse click, it tries to show class members instead.