Added buckets and namespace

Moved all the FcmName style classes into an FCM module so it's now FCM::Name.  Let me know if that's obnoxious and I can back it out.

write_files from fcm-builder is moved into the main namespace of the FCM module which is where the bucketizing is happening now.  There's a FCM.link_nodes that does the symlinking.  Those are the two interesting bits of this pull (amid the namespace refactor clutter).