Pass the Continuum project group id through to Maven builds

Continuum currently passes several properties through to Maven builds, for example:

2009-02-08 07:46:03,716 [pool-1-thread-1] INFO org.apache.continuum.utils.shell.DefaultShellCommandHelper - Executing: /bin/sh -c cd /Applications/continuum-20090207-2059-r741756/data/working-directory/2 && mvn --batch-mode --non-recursive -Dcontinuum.project.lastBuild.state=10 -Dcontinuum.project.nextBuild.number=1 '-Dcontinuum.project.name=Multi Module Example :: Core' -Dcontinuum.project.id=2 -Dcontinuum.project.version=1.0-SNAPSHOT '-Dcontinuum.project.group.name=Multi Module Example' -Dcontinuum.project.lastBuild.number=0 -Dmaven.repo.local=/Users/wsmoak/.m2/repository clean install

The project group name is passed, but not the [Continuum] group id.

I need a property suitable for use in a filename, and although they are both free text, the group name tends to be human readable with spaces, while the group id is not.

We should pass -Dcontinuum.project.group.id=... in addition to the current properties.