MBS-5772: Added support for viewing examples

Adds a list of all examples for a relationship on the relationship documentation
page.
MBS-5772: Rewrite the edit relationship type form for examples

Adds a new 'examples' section which allows relationship editors to specify
examples that can be used for further documentation on relationship types.
MBS-5772: Correctly support adding URL examples
MBS-5772: Allow creating URL relationship examples
MBS-5772: Fix the links to entities in example relationships
MBS-5772: Allow editors to remove all examples
MBS-5772: Move example relationships editor JS to a separate file
Fix /ws/2/json tests

This 'fix' forces the ordering of relation elements in the JSON response which
means that the actual response is consistent with the expected result.

I've also changed some 'TRUNCATE' commands to 'DELETE FROM', as these are faster
to execute.

Finally, there was a bizzare caching problem which was caused by
MusicBrainz::Server loading before 'prepare_test_server' was called, which
resulted in an in memory cache being used for the tests.
Do not update last_login_date when server is read only
Check release events without a country have a date
Merge branch 'release-event-validity'

* release-event-validity:
  Check release events without a country have a date
Merge branch 'mbs-5772-examples'

* mbs-5772-examples:
  MBS-5772: Move example relationships editor JS to a separate file
  MBS-5772: Allow editors to remove all examples
  MBS-5772: Fix the links to entities in example relationships
  MBS-5772: Allow creating URL relationship examples
  MBS-5772: Correctly support adding URL examples
  MBS-5772: Rewrite the edit relationship type form for examples
  MBS-5772: Added support for viewing examples

Conflicts:
	lib/MusicBrainz/Server/Controller/Relationship/LinkType.pm
Merge branch 'read-only-last-login'

* read-only-last-login:
  Do not update last_login_date when server is read only
Merge branch 'json-fixes'

* json-fixes:
  Fix /ws/2/json tests