Migration to MVC

* [x] Introduce JS MVC
* [x] Backbone views and models
* [x] Move pieces of UI code into views
* [x] Plug maps initialization to views
* [x] Load GeoJSON as collection
* [x] Load layer from Backbone collection
* [ ] Plug backpack to collection
* [ ] Plug home favorite/random to collection
* [ ] Fix feedback form map
* [ ] Fix filters on home after nav on detail
* [ ] Navigate between treks and POIs
* [ ] Redirect root url to /t/slug
* [ ] ~~Split layer / data~~
* [ ] ~~Get rid of PJAX ?~~
* [ ] Filtered collection https://github.com/jmorrell/backbone-filtered-collection
* [ ] Refresh results list from collection
* [ ] Get rid of data- attributes in DOM

https://usepropeller.com/blog/posts/from-backbone-to-react/