* Add structure for lists

* Add list timeline streaming API

* Add list APIs, bind list-account relation to follow relation

* Add API for adding/removing accounts from lists

* Add pagination to lists API

* Add pagination to list accounts API

* Adjust scopes for new APIs

- Creating and modifying lists merely requires "write" scope
- Fetching information about lists merely requires "read" scope

* Add test for wrong user context on list timeline

* Clean up tests

* Move ApiController to Api/BaseController

* API controllers inherit from Api::BaseController

* Add coverage for various error cases in api/base controller

- Increase coverage to exercise all parts of each action
- Move into namespace to share common code
- Misc refactor of each action for smaller methods, simpler code