[C++,C#] Support for UGUI and other features.

[TheMajorO]

Changes:

• Implemented support for the new Unity UI system (UGUI) in the C# script "AwesomiumUnityWebTextureUGUI.cs" using the new event system. Additionally you can add Unity's built-in component "Event Trigger" to your GameObject for extra event support.
• Implemented new features in the C++ wrapper that are already available in Awesomium Engine. Namely: Copy, Paste, Cut, Undo, and Redo using system clipboard. As well as for Select-All, Zoom-In, Zoom-Out, and Zoom-Reset. All can be called from "AwesomiumUnityWebView.cs".
• Added the ability to hide Webkit Scrollbars (Both horizontal one and vertical one) without disabling scrolling. This can be done by setting the "HideScrollBars" member flag in "AwesomiumUnityWebSession.cs" to true(default is false) which is in turn used by "AwesomiumUnityWebCore.cs" to initialize newly created Web Views.

Missing features:

• Key Repeat (when keys are held down) is not implemented in "AwesomiumUnityWebTextureUGUI.cs".
• "void RequestPageInfo()" is not working (perhaps it should be removed if not working?). Can be found in "AwesomiumUnityWebView.cs".

[bkeiren]

PSA: Holding off on reviewing and merging this pull request as discussed in issue #6 until further notice by @TheMajorO that the changelist has been cleaned up.