Added the new C++/CLI free parser.

I benchmarked it and it's about the same speed in Release mode (maybe a bit faster) but 3x slower in VS Debug mode due to all the STL usage.
Move all the code in the old parser to the CppSharp::Parser namespace.
Added a bindings generator for the new parser.
Updated the Clix string wrapping code to the latest version with some bug fixes for empty/null strings.
Updated the build for the new parser.