Events Based Logic

Events that allow for logic to be run at specific times such as an event for when a Node is added/removed/moved etc to a graph. Probably from both the graph and node side. 

Possible Events:

Graph Events:
Node Added
Node Removed
Node Moved
Nodes Connected
Nodes Disconnected

Node Events:
Added
Removed
Moved

Port Events:
Edge Connected

Edge Events:
