Modularise root states, closes item:801

First in a long line of overdue refactors to split features by modules.

This way, the app scales better and removes coupling in tests.

See:

* https://github.com/yeoman/generator-angular/issues/109
* https://docs.google.com/document/d/1XXMvReO8-Awi1EZXAXS4PzDzdNvV6pGcuaF4Q9821Es/pub