Remove references to core node actions

[docwilmot]

Unless we implement some code to disable core node actions, at some point someone's going to try and use them and run into that nasty error. So we should add code to remove the core node actions from the UI.

[Graham-72]

I wasn't happy to disable core actions without being sure that they might not be needed in some circumstance. At the moment the UI in the Triggers section only allows for specified assignment options, and these are predefined for core actions in the config file, and so the user does not get offered an invalid option. However, in the Actions section a user can edit the options, at the moment without any limitations. Perhaps the module should include information about invalid trigger-action combinations and not allow a user to set these?

I am also wondering about this for actions provided by contrib modules, e.g. action_example, also twitter_actions. I have provided for an extension of hook_action_info() with a 'triggers' parameter which lists the triggers that can be assigned the action, and I have this working in a test of the twitter_actions module, but I am not sure whether extending this hook with optional data is allowed?