[FEATURE] Extract Alpaca stuff to its own module.

[rosiel]

The Islandora module makes a lot of assumptions about what you're doing with your data. One of them is that you are getting derivatives and/or indexing with Alpaca.

We should extract the Alpaca stuff from Islandora so that it's separate from the collections, files-belonging-to-nodes, and terms-having-URI concepts.

I have done this months ago and called Huacaya (a breed of Alpaca). It likely needs to be updated. In fact we might want to just re-do it so that it has all of islandora's commit history (or at least one commit in common).

Note that not all the Derivative stuff is in here. I wanted to separate out the framework as a kind of library that we could plug into. For example, the AbstractGenerateDerivative class, which specifies the islandora.media_source_put_to_node route would best be in a module that extends Huacaya and assumes that you're using the islandora media-node relation (as well as terms with URIs).

I diagrammed how this could work:
Indexing and Fedora: https://docs.google.com/drawings/d/1ysXqUEigT13wCsYajS0MaaiuWAhxqeCFNey6seiyj2c/edit
Derivatives: https://docs.google.com/drawings/d/1JP6sz164lst8pPP_hNR9Ne7R8qQotzXRwgxelE_DzUY/edit

The goal would be that islandora sites can use the Islandora object structure but not Alpaca. Alternately, a Drupal user could use Alpaca with multifile media, or with any other Drupally way of storing derivatives by making their own Actions that use the extracted Alpaca API ("Huacaya")