Use Rails smart boolean cast to account for values such as "f",
"0", "false", etc. Previously, if a param was present in the request,
it would count as true.

* 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