Add Qt Script Debugger for Windows Builds

The debugger requires mythbackend to use QApplication instead of QCoreApplication.
If you wish to use the debugger in linux, remove all conditions included in this commit and change main.cpp in mythbackend to use QApplication.
Handle Script Exceptions generated in QObjects

Linux & Windows handle the catching of exceptions differently when generated by a QScript.
This code protects all code paths on both environments.

NOTE: This commit only implements fix for Dvr service.  The remaining services will be fixed in a future commit.