Hide or reveal input/output nodes depending on workspace context
Cleaned up logic and extended for more general case
Revive unit tests for hiding/showing input and output nodes
Remove crufty check in CreateNodeInternal that prevent placement of Input/Output nodes
Merge pull request #1937 from pboyer/IOHiding

MAGN-1314: Hide Input & Output nodes in Home Workspace
Add dynamic dispatch for Units on SetParameter.
Connected "Scene" to "VisualizerHwndHost" and "Visualizer"
Merge branch 'master' of https://github.com/DynamoDS/Dynamo into Bloodstone