Fix example case study data

The timestamp on a change history item cannot be the same or less than the main
public timestamp of the content item.
Update case_study publisher schema

Adds rendering_app to the list of required fields and restricts the format types
that are valid.
Merge pull request #6 from alphagov/fix-example-data

Fixes to case study schema and example data
Add unpublishing format publishing schema/example
Merge pull request #8 from alphagov/unpublishing-format

Add unpublishing format publishing schema/example
Remove build_definitions method

it does exactly the same thing as build_string_properties
Pass keyword args to build_schema

makes it clearer what each argument means
Merge pull request #7 from alphagov/schema-conversion

Schema conversion
Extract schema utility functions to module
Frontend schema generator
More explicit fixture builders for links

Use explicit fixture builders to build the expected publisher and
frontend links schemas.

We'll then be able to use these schema builders in the integration tests
as well.
Command line script to generate frontend schema
Makefile for generating frontend schemas
Add auto-generated frontend schema
Remove disallowed properties from the list of required properties

When generating the frontend schema, also remove disallowed properties
from the list of required properties which are output in the frontend
schema.
Validate input schemas when combining
Correction of schema syntax

The 'string' type is case sensitive

When defining the null type, specify the string `"null"` rather than the
json literal `null`
Regenerated after correction of errors in publisher schema

also removed required properties which are not allowed in frontend
schema
Disallow additional properties in links schema of fixtures
Inject available_translations into links hash

.. when generating frontend schema.

Also explicitly test the scenario where the publisher schema may not
have had any links. In that scenario the frontend schema also needs to
insert some schema boilerplate for the links.