Teach git to ignore generated content

Maven adds considerable predictability of where generated files are
stored.  These are of little interest to any SCM since they are
managed by the build process and the results should not be stored in a
SCM.

This patch adds a .gitignore file that excludes the 'target'
directories in the current modules (or sub-projects) from git's
consideration.  Following maven convention, this should be sufficient
to exclude all auto-generated material.

Target: trunk
Requires-notes: no
Requires-book: no
Patch: http://rb.dcache.org/r/5686/
Acked-by: Gerd Behrmann
Acked-by: Albert Rossi