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
MBS-799/MBS-5920: don't allow area annotation or alias editing for non-location-editors
MBS-799/MBS-5920: don't show links that should not be usable to non-location-editors
MBS-799/MBS-5920: disallow editing of relationships that should not be editable by non-location-editors
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.
MBS-6249, Make sure at least one release event row is present when rendering the informatiot tab in the release editor.
Do not update last_login_date when server is read only
Check release events without a country have a date
Merge branch 'mbs-6249'

* mbs-6249:
  MBS-6249, Make sure at least one release event row is present when rendering the informatiot tab in the release editor.
MBS-799/MBS-5920: rewrite Data::Relationship->editor_can_edit for clarity
MBS-799/MBS-5920: factor out editor_can_edit checks in Controller::Edit::Relationship
Merge branch 'areas-limit-appropriately'

* areas-limit-appropriately:
  MBS-799/MBS-5920: factor out editor_can_edit checks in Controller::Edit::Relationship
  MBS-799/MBS-5920: rewrite Data::Relationship->editor_can_edit for clarity
  MBS-799/MBS-5920: disallow editing of relationships that should not be editable by non-location-editors
  MBS-799/MBS-5920: don't show links that should not be usable to non-location-editors
  MBS-799/MBS-5920: don't allow area annotation or alias editing for non-location-editors
Revert ocharles' removal of .links from #sidebar ul
Merge branch 'release-event-validity'

* release-event-validity:
  Check release events without a country have a date