added support for groovy build steps
Merge pull request #41 from CoreMedia/groovy

Groovy Build Steps
Setting next revision
Aligning the new 'existing job' field
Allow system properties to be used when running from the command line.
Take into account new name of field for CopyArtifact plugin
Merge pull request #42 from quidryan/master

Some cleanup
create properties context with job weight plugin