Added archetype for a very basic xproc-based pipeline module

The archetype defines a module with an xproc script that invokes an xslt. It also has a xprocspec test associated with it.

It does *not* demonstrate:
* how to define a pipeline 2 *script* (I think that should be separate from this "basic-module" archetype)
* how to create java-based steps (should be an archetype for java-based steps)
* how inter-module dependencies work (could be an archetype for setting up a multi-module repository - i.e. a script and a utility module where the script depends on the utility module)