Introducing new midonet-parent wrapping project

A new "pom" packaging project is added next to midonet directory
in directory midoent-parent. It is a single pom file that knows
how to build the children projects midonet, midonet.cluster and
midonet.cluster.local. These 3 subprojects are now children of
midonet-parent, while midonet-parent is a children of opendaylight

Commons properties and versions are regrouped in this parent pom
to avoid duplicating around names and values.

All the bunbles can now be build from midonet-parent directory
with a single $ mvn install

Signed-off-by: hugobenichi <hugo@midokura.com>

Refactoring common pom properties in parent pom

Signed-off-by: hugobenichi <hugo@midokura.com>

grouping dependencies versions in midonet-parent

Signed-off-by: hugobenichi <hugo@midokura.com>

using parent pom properties in suboprojects poms

to avoid duplicating names and values around

Adding plugin management