integration with actions module

if the actions and workflow modules are installed, it can be nice to create an action that automatically subscribes a user (or users) to a given node on some workflow transition.

I've written three functions which can be appended to subscriptions.module which enable different actions:

• action_node_autosubscribe_user(): a configurable action to handpick a user to be autosubscribed whenever this action is triggered.
• action_node_autosubscribe_role(): another configurable action to autosubscribe all users in a given role
• action_node_autosubscribe_author(): this non-configurable action automatically subscribes the author/owner of a node.

I've tested these actions against 4.7-1.2, and am releasing all three under the GPL. I would be happy to see them included in the official subscriptions package.