Resolves issue #209

Exit early in RoutedViewHost when in Design Mode.
Added "XDESPROC.EXE" (VS2012 Design Mode) to RxApp list of design
environments.
Also fixed an issue in RxApp where checking for design mode was testing
against full path of assembly instead of just the assembly name.
Merge pull request #214 from jordansjones/master

Addresses issue #209.