Actions API :: Two methods

 - Actions() takes a list of ActionTags and finds corresponding Actions
 - FindActionTagsByPrefix() finds ActionTags matching given prefix
Merge pull request #1199 from johnweldon/3-action-api-refactor

Actions API :: Add Actions() method to return Actions by ID

Now that we have UUID identifiers for Actions, allow retrieving by ID

(Review request: http://reviews.vapour.ws/r/510/)