Maslow: create editor, admin permissions
Grant editor perms to all current maslow users

Before the introduction of permissions into Maslow, anyone with a `signin`
permission can perform any change within the app. Once permissions are live,
then anyone with the `signin` permission can view only.

In order to preserve editing for the users who have been entrusted with that
ability up to now, all Maslow users get the extra `editor` permission.
a
Merge pull request #216 from alphagov/grant-editor-perms-to-all-maslow-users

Grant editor perms to all current maslow users