[SharpDX]comment fixes.

at Matrix.cs
[SharpDX] Add comments

to ViewportF class
[SharpDX]Added comments.

to Viewport.cs(also added Validate methods).
[SharpDX] Comment fixes.

+ small fixes to Viewport
[SharpDX]comment fixes.

at ViewportF.cs
[SharpDX]comment fixes.

at Viewport.cs - final
[Toolkit.Input] Implemented pointer input events for WinRT platform
[Toolkit.Input] Replaced Point struct by SharpDX.DrawingPoint
[Toolkit.Input] added comments for Pointer* classes.
[Toolkit.Input] Handle pointer input for Desktop platform (mouse only)
[Toolkit.Input] made a few methods static
[Toolkit.Input] added pointer input sample for WinRT platform
[Toolkit.Input] added sample pointer input projects for Desktop platform
[Toolkit.Input] Added comments to PointerPlatformDestop class
[Toolkit.Input] Implemented basic touch support for desktop platform
[Toolkit.Input] fixed compilation for net20 profile
[Toolkit.Input] Merged PointerPointProperties in PointerPoint
[Toolkit.Input] Deleted unused PointerPointProperties file
[Toolkit.Input] Refactored pointer input for Desktop platform
[Toolkit.input] Refactored pointer input for WinRT platform