Until now all the server-side plugins have been associated
to a single jar file in the /plugin directory.
As first step to allow different forms of plugins
(e.g. script files, directories or anything else that
can provide classes and resources) we need to de-couple
the underlying Jar file from the server side plugin.
We introduce the concept of "plugin-scanner" as the interface
to scan the external form to discover:
- plugin classes
- plugin resources
- plugin meta-data (i.e. Manifest)
Change-Id: I769595a030545a5f272f453c3cf435b74719e1e7
a0c3ba5a4d