org logos in list-view templates; org logo,title in detail pages

Added organization logos wherever objects are listed or displayed.
Logo URLs are derived from object ID and have a standard form:
    http://MEDIA_URL/REPO-ORG/logo.png
added logo and title,description to organization detail pages

Previously this view redirected to /collections/.
Now it displays basic info about org and a list of the org's
collections.
support functions for org-specific base templates per domain

We want to be able to support organization-branded versions of
the DDR.  Partners will want to display their collections (and
only theirs) and customize the UI.

settings.ORG_DOMAINS is used to list domains that belong to
specific organizations.  If the request domain matches an
organization domain the org keyword is added to sitewide context.
If org-specific base template exists it also is added.
mv functions from context_processors to ui/__init__
templates extend BASE_TEMPLATE from sitewide context
"org"->"partner" for less confusion; domains_org only returns org

- Outside of the domain_org and base template functions, refer
  to "partner" instead of "org" or "organization", since these
  are already used.
- Calling functions use the org/partner from domain_org but not
  the domain, so only return the org/partner.
__repr__ methods so the models look nice in tracebacks
collection/entity/file views filter by partner, if present

If ui.domain_org finds a partner,
- Collections list pages only list that partner's collections
- list and detail views raise Http404 if a different partner
  is requested.

NOTE: facets and search results are not yet filtered!
sample base templates for hmwf and janm
added clickable list of orgs at top of collections list page
organization logos everywhere on collections-list page

Better too many than too few I guess...
rm HMWF partner template
generic partner-branded base template and mods to tmplt chooser

- ui.choose_base_template can now return a generic partner
  template (e.g. ui/base-partner.html) in addition to the master
  and partner-specific templates.
back-end changes to partner-branded site functions

- Use settings.PARTNER_DOMAINS instead of ORG_DOMAINS for
  terminological consistency.
- ui.domain_org returns tuple (repo,org) instead of just org
- Helper function for filtering views by partner if partner is
  present.
more appropriate display for partner-branded collections-list

No list of other orgs when showing a specific partner's objects.
get jquery from Google APIs instead of locally
filter search and term-query results by partner
faceting.Term object
facet term page w description, parent, children, search results
faceting.Term object