Load into M2E, update to Java 7

The changes fall into a few categories:
1) top level pom has a few updates to update the source/target to 1.7 to make the rest of this actually work
2) Update the lifecycle-mapping stuff to actually run some of the plugins so that code is properly generated
3) Change from the jaxb-maven-plugin to CXF's xjc-plugin (which works with java8 without the system property hack).  CXF's xjc-plugin has the lifecycle stuff built in.
4) Add build-helper plugin to make sure the generated dirs are added all the time so that m2e picks them up.

With the changes, you can git clone a clean activemq and pull it directly into eclipse (providing you have all the scala stuff installed), do a quick Maven -> Refresh Projects (not sure why that is needed), and it all builds without any errors.