Allow speeches to have a person override for non IG people

This allows editors to type in a person who isn't on IG, and skips
edition role appointment validations.

The feature is persent when the checkbox controlling the display of the
override box is checked, the value of the speaker is cleared when
unchecked.

Limitations: They are not people so non of the fuctionality associated
to people exisit, images, search indexing, their own pages etc.
Add in fontend test for person_override on speech
admin controller speeches tests for person_override

Move speech type outside of the loop and add in missing details to the
person_override section
Speech unit tests

Also fix search_index on speech for person_override
Method provided by AR
Add back missing break tag
refactor _speech_details parital
Clear the role_appointment_id in the controller and fix label
Merge pull request #488 from alphagov/speeches-by-other-people

Allow speeches to be given by non IG people

https://www.pivotaltracker.com/story/show/40773995