always put Cheshire3 Session in context for templates

Allows templates to be called in much cleaner way, without specifying
session in context every time.
listThing returns list, iterThing return iterable

Previously listThing functions were generators, so actually returned
iterables.
moved contributor selector out to own template

Created a new template `searchContributor.html` that generates the
search within contributor selector. This template is self-contained
requiring only `session` from context, so added benefit is that you don't
need to supply the list of contributor when calling any template that might
include the selector. This makes calling code much cleaner!
make contributor selector available as page (e.g. for SSI)

Make the search within contributor selector available as a page, this
allows it to be included in other pages dynamically via Server Side Includes
or a similar mechanism.
enable search within without additional search terms

Enabled search within collection and search within contributor
features to be used without specifying additional search terms.
This allows for display of all items within a collection or from a
contributor.
improved query summary

Improved display of query summary when search/filtering by
collection or contributor
make facets and facet name configurable
add AA to always capitalized
use clever title casing in search facets