Moving plexus component metadata dependency definition into parent pom

Cleaning up the plexus-component-metadata dependency by moving the
definition into the plugin management of the parent pom and only
reference it in the modules.


Change-Id: I2878319363842e476e023a8de155f6cec4a08244
Signed-off-by: Martin Schreiber <m.schreiber@bachmann.info>