With the permission of Romain Degez, CTO of Smartjog.

Signed-off-by: Sébastien Luttringer <sebastien.luttringer@smartjog.com>

Uses a fork and permits to set ionice on child.

/!\ Don't use logging for logging as it would (maybe) end in a deadlock for the
child.

Handles correctly termination.

Harmless renaming.

JobManager + BaseJob.

Initialization, re-authentication...

 * tags not working properly
 * log messages
 * typos, indent, comments
 * etc...

 * md5 hash of transfered file is not faked anymore
 * implemented job cancellation
 * xfer tcp ports were not released, exhaustion was possible