Refactoring to eliminate phantom method calls.

Looks like some old code was calling a modele method that
has not existed for some time.  UnitsFilter is nowhere to be
found here or in Hydraulics.  Replacing with test that AFAIK
will duplicate the functionality described in the comments.

Also adding a virtual attribute 'mime-type' for MasterFiles and
subclasses, as that was being called deeper down.

All of this is to facilitate Hydra.desc(bibl) calls where we
are building MODS records based only on database information.
fixing URL to Solr cores
allow editing of index destination on bibls
Try passing bibl.discoverability parametrically

The XSLT indicates this may be a deprecated method, but we have
a need to occasionally push shadowed bibl records to Solr.  This will
need further refinement.
default text for bibl.index_destination == nil
hotfix
Hotfix: reading IndexDestination from Components

This is to accord with new practiced in Solr production, which
require a field 'released_facet' flagging a record for copying
into another index.  As Component Solr records are built via a
call to a Fedora disseminator, this value is passes parametrically
in the HTTP request.

TO DO: migration to ensure Components belong to an IndexDestination
Now importing JP2 from iView Catalogs

Also pushing jp2 files to Digital Library, and adding transcription
text when available from the import folder.
Merge branch 'masterfile-jp2' into production
Merge pull request #177 from uvalib-dcs/production

Production fixes from Jan-Feb