C# support

This adds C# support to nano. The nanorc can be split up a bit, and since it's just rejigged java.nanorc, some work on making it more C# native would be nicer. It seems to highlight my code fine though, so I'm pushing it.
![2013-03-23-172714_490x338_scrot](https://f.cloud.github.com/assets/3161292/294558/39ebd42c-93f8-11e2-9571-8de65f9bd97c.png)