Rerun command can rerun multiple failed jobs

We can now automatically choose multiple failed jobs
for rerunning.

The selection of the failed jobs to rerun are:

- Timeframe in which the failed jobs were scheduled
  -> specify "days=" or "hours="

- Jobs newer than a certain jobid (the given jobid is included)
  -> specifying "since_jobid"

Fixes #168 : Enhance rerun command to be able to restart all failed jobs from last n days

Signed-off-by: Marco van Wieringen <marco.van.wieringen@bareos.com>