Addition of the Cache + registration of methods to add and delete elements in cache
Merge branch 'BetterElementTracking' of https://github.com/DynamoDS/Dynamo into ElementUpdateIssueFixes
Add in tracking of whether an element has been foreign deleted
Add protection into the vis manager to stop it crashing on corrupted state which is making debugging slower. This may need to be removed again
Protection checks in the Viz pipeline as to whether the objects are still alive before trying to draw them
Merge pull request #1528 from DynamoDS/ElementUpdateIssueFixes

Element update issue fixes