Removes src.xml used building src tgz via hbase-assembly. Use git archive instead going forward. Updates developer release candidate documentation and the make_rc.sh script. Signed-off-by: Sean Busbey <busbey@apache.org> Signed-off-by: Peter Somogyi <psomogyi@cloudera.com> Signed-off-by: Mike Drob <mdrob@apache.org>