Bug 30982: API tweaks

Bug 30982: API tweaks

This patch makes the following changes to the 'background_jobs' API:

* We now call them 'jobs'
* Removed deprecated query parameter definitions
* Added only_current query parameter
* Controller gets adapted to use $rs->filter_by_current when
  only_current is passed

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>