Add .NET config files as XML
Fix package.config to packages.config
 add pants BUILD file highlighting to languages.yml

the pants build tool uses python files named BUILD. This adds highlighting for them.
Merge pull request #1657 from techniq/patch-1

Add .NET config files as XML
Merge pull request #1653 from baroquebobcat/patch-1

add pants BUILD file highlighting to languages.yml
Add F# sample.  Add Forth extension .fs.