Moving SyntaxTree parser code to the Mono Engine

This fixes #704

Note, I also changed the ToolVersion from 12.0 to 4.0 on the ScriptCs.Engine.Mono.csproj.  Now it's the same tool version as the other projects.  Mainly so I could do this work on my MonoDevelop/Ubuntu box ... which is awesome :)

You might want to do <code>git clean -fd</code> as git will not remove the folder structure for the removed ScriptCs.SyntaxTreeParser project.