Add include paths to props for visual studio

The paths added are:
$(ProjectDir)ZeldaDS\arm9\source -> game and external code
$(DEVKITPRODIR)libnds\include -> devkitPro NDS code

Unfortunately, $(DEVKITPRODIR) is a props macro that is hard-coded to C:\devkitPro because I can't figure out a way to get this path easily. There is a DEVKITPRO environment variable, but it's in unix format.
make_package.bat now uses VS2010 compiler instead of VS2008, and package folder is gitignored