Got TaskDialogIndirect working properly.

After almost 2 weeks of research and condensing the Windows API Code
Pack I finally got the exact dialog I want working!

Changes:
1) Added TaskDialog.cs which is a condensed version of the Windows API
Code Pack (Vista Bridge) minimized to my very specific use case.
2) Put the StatusDialog in a delegated thread like I did with MessageBox
to avoid any delays with the UI.
3) Tweaked EnableThemingInScope according to the VS2012 code analyzer.
During testing of TaskDialog I ran into an exception with
DeactivateActCtx so I threw in a try/catch to quickly fix it without
really understanding the exception. Sorry I didn't save the exception.
4) Pretty much re-write StatusDialog.cs to use the new TaskDialog.cs.