Added missing include required for min<>()
Added linebreaks to improve readability
Restoring original working directory when done

I find it irritating to be in a different directory after calling a batch file.
Use paths relative to batch file location

This way, the batch file works no matter from what working directory it was called.
Now, it can simply be started via double-click.
Deleting old project files without asking first.

Also, we won't try to delete the target directory if it doesn't exist.
This way, we avoid an irritating error message about a directory not existing.
VS target version can be selected via command line argument.

Valid values are vs2008, vs2010, vs2012, vs2013. The output directory is chosen accordingly.
Default value is vs2012.
Updated README.md to reflect changes in create-projects-win.bat
Merge pull request #826 from DanielSWolf/missing-include

Added missing include required for min<>()
Merge pull request #827 from DanielSWolf/cmake-tweaks

cmake tweaks