Provide packed jars in update site

Provide packed jars in update site

This is recommended to use in eclipse p2 repositories to reduce bandwidth.

If we need to provide a zip of the update site in the future, we should
consider the workaround done by CDT to reduce the zip size, see
https://git.eclipse.org/r/#/c/39624/

References:
https://wiki.eclipse.org/Tycho/Pack200
https://wiki.eclipse.org/SimRel/Simultaneous_Release_Requirements#Provide_optimized_p2_repository_.28partially_tested.29
http://build.eclipse.org/simrel/mars/reporeports/reports/pack200data.txt

Change-Id: I80de8ccaf96c6741db890e079c590ea101e88a9d
Signed-off-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/41114
Reviewed-by: Hudson CI