SwapChainRenderTarget  leak resources.

This one leak windowHandle resources. ('User objects' at Task Manager).
After 10000 or so the App crash.

`SharpDX.Utilities.Dispose()` can't be used on `_swapChain`, maybe
remove `readonly` modifier?
Reduce Garbage on TouchPanelState.GetState()

-Reduce the garbage generated by  TouchPanelState.GetState() .
GetState()  was generating garbage at a constant rate of 12Bytes/Frame.
Remove readonly & call SharpDX.Utilities.Dispose() on _swapChain