Unifying the library namespaces.

Now all classes in the library have a single namespace, HTFM.Library (it's better for it to have an indicative name, right?).
This will save us trouble: the library classes won't need to import any other library class, and the web part will just need "using HTFM.Library".

TODO: In the web part, I've fixed the import directive in Default.aspx and groups.aspx, but both still call a non-existent method. Someone fix that.