This removes all logic from the search form Blade template, and extracts
it to the "Controller" level via Sage's filter system. It also adds a
global 'app' filter to hook into, so that the search form data will be
served on every page.
* Resolves issue with WP only looking one-level deep for templates #1870
* get_template_dir() and related functions now point to sage/resources
* Use collect() when assembling views paths
* Update tree in README
