Remove unnecessary view + helper overrides

[cbeer]

The advanced search forms, facet + constraint overrides, and multi-select fact query building are now present upstream in blacklight and not needed here. After this PR, the remaining functionality in this gem is:

• parsing boolean queries within a search field
• "legacy" redirects from old adv search queries to the newest style
• "customization" of the solr query used to construct the advanced search (using form_solr_parameters etc)

Upgrade guide

1. Remove advanced search controller + helper overrides. (e.g. include BlacklightAdvancedSearch::Controller in CatalogController)
2. Remove advanced search js + css assets (//= require 'blacklight_advanced_search' in app/assets/javascripts/application.js)
3. Add legacy url redirects, if appropriate to your application:

   before_action BlacklightAdvancedSearch::RedirectLegacyParamsFilter, :only => :index

TODO:

• [x] https://github.com/projectblacklight/blacklight/pull/2753