CloseTabCommand should work /better/. All TabControls inherit from BaseMetroTabControl in order to make extending the TabControls easier.
Reworked TabItem Close button infrastructure. Close Button isn't show until the tab is selected or has mouse hover. CloseTabCommand is only called on MVVM Data Bound items.
Added a TabItemClosingEvent where the user can cancel the closing of a TabItem for non-databound TabItems.
A MetroTabItem is only auto-generated from data bound items.
Fixed the TabItem datacontext issue for now. Temporarily worked around the TabControl Unload issue.
Added TabStripPlacement to the Metro*TabControls that did not have it. Fixes #527
Oops, forgot to remove the TabStripPlacement from MainWindow.xaml.
Merge pull request #520 from Amrykid/metro-tabitem-patch2

[RFC] Metro TabItem/TabControl Patch #2