Don't add filters just by including SearchContext.
This allows the use of Blacklight::Base (which includes
Blacklight::SearchContext) onto controllers that aren't including
Blacklight::Catalog without adding unneeded filters.  If an implementer wants to
use the filter, they can use `record_search_parameters`.
Merge pull request #805 from projectblacklight/record_search_parameters

Don't add filters just by including SearchContext.