MH-10357, gstreamer-service-* missing from main pom.xml

The gstreamer-service-* modules were removed from the main pom.xml file
when the analytics and export modules were removed making it impossible
to build them from the main pom. Especially, a
  mvn clean install -Dall
will not build them anymore, meaning that most people probably wouldn't
notice if there were any build errors.

This commit will add these services to the alternatives profile in the
main pom.xml file.

Notice: This patch already went into r/1.5.0 but was lost in a merge
conflicts when the branch was merged back into develop.

Signed-off-by: Lars Kiesow <lkiesow@uos.de>