Added CiviRules Action Display Message. Allows a custom message to be displayed to the user on conditions.

refactor of trigger data handling so that custom data from within the prehook becomes available in trigger data. It was also needed to add a hook for altering trigger data

Please see issue #47 here: https://github.com/CiviCooP/org.civicoop.civirules/issues/47

refactor of trigger data so it would always include a contact entity and changed the entity tag triggers