Introduced skeleton classes: BillboardText3D, BillboardTextModel3D
Introduced a new "BillboardVertex" data type
Added initial implementation of BillboardTextModel3D, BillboardText3D
Introduced "RenderBillboard" render technique
Undo changes in HelixToolkit.Wpf.SharpDX_NET40.sln
Merge pull request #1 from Benglin/master

Initial implementation of billboard text support