Automated build and removes binary files from Git

Okay, I couldn't take it any more, I don't like seeing nupkg binary files in Git! :-)

So I've added a build folder and replicated your build process as I understand it.
The canonical way to update version numbers now is to change them in build.bat. Running it will update your assemblyinfo files and generate the nupkg files for you.

Make sure to test this PR out first to make sure that I took the correct files to include in the NuGet packages, from what I can tell the packages are identical to the ones you've released.

The MSBuildCommunityTasks files are unaltered from their downloaded version so you can ignore those, they're not important.

Any questions, let me know!