Pages in views

My conception of how to address #7543.

TODOs:
 - [ ] Convert plugin page handlers to the same format
 - [ ] Rewrite commits to fix typos (the initial commit should be the routing component)
 - [ ] Don't expose segments array to resources views (use set/get_input instead)
 - [ ] Move breadcrumb building into resource views ([see](https://github.com/Elgg/Elgg/pull/7679/files#r21842694))
 - [ ] test thoroughly