[KARAF-2160] Add option to only create tar.gz or zip archive in CreateArchiveMojo (thanks to Christoph Gritschenberger for this patch)

Signed-off-by: Andreas Pieber <anpieber@gmail.com>

git-svn-id: https://svn.apache.org/repos/asf/karaf/trunk@1442067 13f79535-47bb-0310-9956-ffa450edef68