roles refactor (renamed _OTHER)

EDIT_OTHER is now just EDIT
DELETE_OTHER is now just DELETE
... etc.
implemented RightsHelper::userCanAccessMethod()

the userCanAccessMethod is the authoritative place to define the permissions for a particular API method.
See https://trello.com/c/p3k8vmoq/294-define-user-authorization-rules-for-each-api-method for details
removed parameterization of current user id from most commands (unless they need them for more fine-grained permissions checking)

this was my former idea of implementing security for every method, but I decided against it in favor of checking at the JSON RPC server level.  the code is cleaner this way too.