Contract level events

[RitaMAllenCA]

This is a much desired feature in the community. Host-enforced contract level events. Needs grooming.
The objective is to have a way to track the event and the contract that generated the event and on the host side, create an irrefutable record.

The implementation should support the following functionality:

1. What events did a given contract generate - irrefutably
2. Node can ask EE what events a given contract emit? (new endpoint)

Implementation notes (to be updated by the dev once the implementation is complete):

• Create a new bounded length event type
• Update the FFI to take a string (event-generated message) & origin (contract identifier) --> and record it on the host side so there is an irrefutable record of the event.
• Create a new endpoint in node to report which events a given contract generated.