Move satcmd to other repo and distribute saturnin as a stand-alone
shellfu library.  Users can import just the library instead of
embedding it inside their source tree, which enables them to delegate
part of the job to package manager.

The new Shellfu brings some large changes.  Among what touches us
directly:

 *  Most global variables were renamed (removing SHELLFU_* prefix).

 *  inigrep API has been revamped and the file merging/guessing
    feature has been dropped; it now belongs to us.