Rename file to better communicate purpose
Introduce a new dedicated Controller for taxonomies
Avoid strict notices by making these requirements looser
Pluralize for consistency
Basic test coverage for taxonomy route registration
Fix undefined variable
Fix invalid variable
Move taxonomy test coverage to its own class
Test preparing a taxonomy

Oh yeah red lines!
This now forever shall be known as the `WP_JSON_Terms_Controller`
Restore our term test coverage
Normalize error codes for terms
Routes should include the namespaces
Ensure term count is returned in the response
Always return terms
For now, we aren't returning objects arbitrarily embedded in other
objects
Localization functions
Break into blocks
Pass the entire request object

We don't need to worry about backwards compat because the filter will be
renamed anyway

See https://github.com/WP-API/WP-API/pull/579/files#r19854535
Properly register these endpoints