Allow minion backend to be configured from the conf file

[mbroadhead]

Currently we are forced to use the Minion::Backend::File backend, which is depreciated (see #15). It would be nice if we could provide our own minion backend from the configuration file.

Instead of:

{
  minion_db_file => "./minion.data",
}

We could do:

{
  minion => { SQLite => 'sqlite:test.db' },
}

OR:

{
  minion => { Pg => 'postgresql://postgres@/test' },
}

This would allow users to use any Minion backend that they want, without having to modify the rex-jobcontrol source code.

[ehuelsmann]

This has been implemented yesterday on the master branch. Thanks!