add: Visual Studio 2012 project and solution files
change: ignore intermediate and output files from build

Note that project relies on environment variable NUnitBin to find NUnit dll and GUI runner.
All unit tests pass.

add: embedded resource text file for unit tests
fix: use System.Environment.Newline, not '\n'
Switch to .NET 3.5

(to allow breakpoints via NUnit GUI)
Merge pull request #1 from yoyobbi/dev.vs2012

dev.vs2012 - Visual Studio 2012 support