Honor PROGUARD_HOME.

This needs to be set for Visual Studio to find the right JAR.  Otherwise proguard.bat fails.
Windows: Escape mono platform jar path.

We need to escape the path in windows according to the rules of proguard.bat
since mono is typically installed under C:\Program Files (x86)\Reference Assemblies\
Merge pull request #4 from kjeremy/visual_studio_fixes

Visual studio fixes