Updated POM; P4Java is now in Maven.
Merge remote-tracking branch 'upstream/master'
Custom build args for Workspace names.

Takes `${parameter}` and replaces it with the value if defined or uses
the tag (`parameter` in this case).
Includes substitution for a space ` ` with `_` as per P4 behaviour.
Merge pull request #6 from p4paul/master

Fix for the 'DELETE generated files' option