[KARAF-2094] Extend wrapper docs by JVM param FAQ

Signed-off-by: Andreas Pieber <anpieber@gmail.com>
(cherry picked from commit b76c98b70f0a2aa1448c77e013b003af1e9d3e42)

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

git-svn-id: https://svn.apache.org/repos/asf/karaf/trunk@1427789 13f79535-47bb-0310-9956-ffa450edef68