Rename module loading commands

These had the "cmd_" prefix which we generally only use for RFC commands. The
names have been changed to match the other core oper commands.
ratelimit: Use txircd's util functions
cmd_rehash: Prevent an exception on server rehash
SQUIT is an RFC command and should probably be moved to that directory
Fix an inconsistent file ending
Refactor variables that shadow built-in names

Python doesn't care in most cases, but still something that should probably be
avoided if possible
Remove unused imports
Nuke TestServ
Merge pull request #97 from Heufneutje/fix-many-things

Various fixes