Changes

releng: add b3 aggregator for generating a maven repository

This project creates an maven repository with all dependencies needed
for Trace Compass features. Right now, TMF, CTF, LTTng Kernel, UST and
Control are installed. The location of the generated maven repository
by default is ${user.home}/build/final. This can be changed in the
tracecompass.aggr file.

See link below for more details
https://wiki.eclipse.org/CBI/aggregator/manual

Change-Id: Ia75cfffd9deaaa6e0492ea4ef838c77fc6b94e8c
Signed-off-by: Bernd Hufmann <Bernd.Hufmann@ericsson.com>