Enforce maven 3.0.5+ to build droolsjbpm

Reasons:

• To have stable, reproducible builds, it's important that no one is building this our project with bugs that already fixed in a newer maven version (while others don't see those bugs because they build with the latest).
• Also see the dangerous issue described on thecore list: "mvn 3.0.4+ vs 3.0.3 - different dependency resolution ?!"

TODO list:

• The change itself in the sources is simple. Open droolsjbpm-parent and change the enforcer-plugin like this

                    <requireMavenVersion>
                      <version>[3.0.5,)</version>
                    </requireMavenVersion>
  

  Notify porcelli to do the same for uberfire.

• Bigger issue is communicating this change to the team. Expect that many people still to use 3.0.3 and 3.0.4 and suddenly "won't be able to build". Send them an advance notice before pushing the change. Expect some people not to read that and to complain anyway - so push early in the morning and watch the IRC so you can help them
• Last, but not least: configure all jenkins jobs for droolsjbpm master to use maven 3.0.5 or they 'll start failing.