Added a style for DataGrid
Updates to DataGrid style including styles from stefan-schweiger. Update
to match Azure DataGrid styling.
Update column header style. Add disabled style.
Update DataGrid styles to use Gray brush resources instead of color resources. Make the default DataGrid style more like stefan-schweiger's. Add Azure DataGrid
style as a separate resource.
added control to demo
missing resource
dropped AzureDataGrid style while working out what to do with it
Calendar respecting dark/light theme
Reverted change to Virutalizing ComboBox because it breaks grouping

Last change set the itemspanel to virtualizing but this breaks the grouping behaviour of the combobox
fix flickering Issue #419

fix the nasty flickering at window starting.
Merge pull request #475 from punker76/master

this is the fix for the nasty flickering window in Issue #419
fix showing border without glow brush

this happens, if a window has no glow brush but a border brush and
border thickness.
tweaking demo layout
Merge pull request #474 from stefan-schweiger/patch-2

Reverted change to Virutalizing ComboBox because it breaks grouping
Merge branch 'master' of https://github.com/vegar/MahApps.Metro into vegar-master
Merge pull request #473 from MahApps/daveraine-DataGridStyle

 DataGrid Style - Extends #446, Resolves #377