Collapse indicator_from_(raw|event|domain) into one function.

Provide an indicator_from_obj view which is designed to be used with
AJAX requests. This allows us to remove indicator_from_raw,
indicator_from_event, and indicator_from_domain views which were all
doing the same thing.
Remove add_indicators_for_domain.

This now uses the create_indicator_from_obj() handler. This requires
moving the new_domain assignment out from a buried conditional.

While here, fix a bug in add_new_domain() which was passing None as IP
type.