Resolved JERSEY-1839.

- added support for customisable Jersey runtime thread factory management.
- presently supported on the server side only.
- introduced an common internal background task scheduler (ScheduledExecutorService) injectable using a @BackgroundScheduler qualifier.

Change-Id: I80270fa2cc71f27460cdcfd93dbdacc51bf39bab
Signed-off-by: Marek Potociar <marek.potociar@oracle.com>
Merge "Resolved JERSEY-1839."