Added code to make the Expander control have a disabled look.
Added mouse over and pressed effect to the expander toggle button.
Fixes #1270
Merge pull request #1267 from Tide/ExpanderDisabledFix

Fixes #1266
expander style xaml formatting
use BackgroundToForegroundConverter in expander style
GroupBoxHeaderForeground default to null like expander (can be overwritten)
set version to 0.13.0.0
Update 0.13.0.md
Merge pull request #1277 from Tide/1270.DialogAccentFix

Fixes #1270
xaml formatting for dialog styles