DataGrid Style - Extends #446, Resolves #377

I've rebased #446 and have integrated it into the new demo app

A couple of little visual things to sort out:

 - [x] should the header borders be thinner/lighter?
 - [x] do we want to ship the `AzureDataGrid` style in the box?

Also has 075fd42 which resolves the scroll viewer being visible for the AnimatedSingleRowTabControl control.

Test it out, let me know your thoughts.