Implement Storage Provider Manager Interface

[ryanrutan]

Includes filling out the StorageProvider interface

[ryanrutan]

See:
https://community.jivesoftware.com/docs/DOC-127831#comment-2266742
integrated this contribution on 08/18/2014, testing still to come.
Also added a jive.addon.storage.feature [disabled|enabled] feature to the jive-addon/pom.xml to control if it shows up in the definition.json, as storage providers require admin access. Default is disabled.