Rename SwapChainBackgroundPanel

References to SwapChainBackgroundPanel are currently named
'SwapChainPanel' (and sometimes 'swapPanel').

DX11.2/Win8.1 introduces a new UIElement,  'SwapChainPanel'.
http://msdn.microsoft.com/en-us/library/windows/apps/bg182880.aspx#three

I renamed all SwapChainBackgroundPanel because having then referred as
swapChainPanel could be confusing in the near future.

Arguments become -> 'swapChainBackgroundPanel'
Properties become -> 'SwapChainBackgroundPanel {get;set;}'
fields become -> '_swapChainBackgroundPanel'
Merge remote-tracking branch 'upstream/develop' into tnc_Rename_SwapChainBackgroundPanel
Merge remote-tracking branch 'upstream/develop' into tnc_Rename_SwapChainBackgroundPanel
Merge remote-tracking branch 'upstream/develop' into tnc_Rename_SwapChainBackgroundPanel
Merge remote-tracking branch 'upstream/develop' into tnc_Rename_SwapChainBackgroundPanel
Update XamlGame.cs
Merge remote-tracking branch 'upstream/develop' into tnc_Rename_SwapChainBackgroundPanel
Merge remote-tracking branch 'upstream/develop' into tnc_Rename_SwapChainBackgroundPanel
update recent changes
update changes
-update changes
Merge remote-tracking branch 'upstream/develop' into tnc_Rename_SwapChainBackgroundPanel
Merge remote-tracking branch 'upstream/develop' into tnc_Rename_SwapChainBackgroundPanel
Merge remote-tracking branch 'upstream/develop' into tnc_Rename_SwapChainBackgroundPanel
same for Guide.cs
fix for DirectX.cs
fix comment
fix comment
Merge pull request #2070 from nkast/tnc_Rename_SwapChainBackgroundPanel

Rename SwapChainBackgroundPanel