Updates and bug fixes

Touchpad's SetWindow/SetForm methods now accepts a parameter to control the technique used to perform the render, event-based (old technique) and poll-based (used in @brandonscott's razer-notes app).

DrawWindow has been modified to (hopefully) be more efficient and use less memory.

Now targets .NET 4 (unknown if this was an issue, but recent compilations failed due to it targeting 3.5).

Fixed callbacks supplied to Touchpad.EnableDynamicKey not being fired properly if no previous state was set.