Add format advice for main types.
Add format advice for subtypes.
Add policy supporting page advice.
Remove deprecated / protected subtypes from lists.

Side effect:
This will force editors / speedtaggers to choose
an alternate subtype if one of these is already
selected, which is something currently covered via
validation.
Use source-agnostic wording for speech role.
Remove special case for DetailedGuide in tests.

Detailed guides have their create button back.
Whitespace.
Change call to action for format advice.
Hint at which subtype is selected in the advice.
Cap the width of the format advice.
Merge pull request #917 from alphagov/inline-guidance

Inline guidance to writers for usage of all format types