Validation feature complete

Validation is now feature complete, at least for the features that I thought of :D.
Added a sample page for Gestures.
Added a sample page for Validation.
Added user extensibility to the Validator list.
Refactored Validation into it's own namespace (Validation)
Renamed classes to make validation Xaml easier to read/create
Added property setters to actions
Enabled generic actions
Added system converters for Color,Rectangle,Constraint,Font,GridLength,ImageSource,Keyboard,Point,Thickness,Uri, and WebViewSource.

![image](https://cloud.githubusercontent.com/assets/3757116/4966145/183dd168-67af-11e4-81dc-eb9326ba8e54.png)


I'm sure there is at least one or two features I've forgotten just now.  I'll get the documentation going in the morning.