Only set a DisplayName binding if one doesn't already exist
Start on MessageBox
Simplify MessageBoxViewModel quite a bit
Document MessageBox and friends
Start writing unit tests for the MessageBox stuff
Add more unit tests for MessageBox, and convert to use more system types
Merge branch 'feature/messagebox' into develop

* feature/messagebox:
  Add more unit tests for MessageBox, and convert to use more system types
  Start writing unit tests for the MessageBox stuff
  Document MessageBox and friends
  Simplify MessageBoxViewModel quite a bit
  Start on MessageBox
Make MessageBoxView.xaml a bit more faithful

Just a little bit of vertical alignment to go
Style MessageBoxView a bit more.

BoolToVisibilityConverter can now handle any data type
Use MessageBox in the integration tests and samples
Allow MessageBox users to override text on individual buttons on a per-case basis
Write tests for the updated BoolToVisibilityConverter