Remove name mangling from FileSystem typeprovider

This addresses issue #11, and provides the API desired by @forki, namely
FS._fszmq.Path and FS.fszmq.Path (perfectly matching the file system).  It eliminates the name mangling done within the ProvidedTypes.fs file, and reimplements the nestedTypes with our own naming, which should cause the folders (and the files) to perfectly match the file system in all cases now.