quick zoom tool is missing region marquee

[IngoClemens]

Currently the quick zoom tool misses a marquee style display of the region the user wants to zoom into.

Because the tool is based on the standard draggerContext there no such option.
To draw a marquee a custom context plug-in needs to be written but currently the python API of Maya doesn't seem to provide this.

A solution would be to write a c++ plug-in but this would require recompiling for every Maya version which seems like too much work for a zoom tool.

Maybe someone has a better approach to make a selection box visible through python.