Separate the proprietary / non-proprietary deliverables for each connector

As we have spoken today this ticket is dedicated to try to work on the build process to separate proprietary and non-proprietary libraries in the release package.

In this way, for example, we could have a standard way to release a specific library for the connector (mcf-alfresco-connector) without release proprietary libraries and allow users to add proprietary libraries in a specific folder "connector-lib-proprietary" that could be added to the ManifoldCF classloader.