Added a trigger to react when an activity date is reached and added an action to update the activity status

Fixed #88 delay an action based on the data in triggerData. And added a delay for contribution to delay to xth day of the month of the contribution

Fixed #89 possibly to check whether a condition or action is valid in a certain rule setup or with a certain trigger

This stops an empty api request from being made and causing an error.

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