Creating subgraph from selection now works
Add subgraph manager so subgraphs can be shared across subgraph nodes (this breaks everything but I've gotta figure it out either way)
Give subgraphs a context
Subgraph manager sets graph for new subgraph context and sets context for their node manager
Fix subgraph saving
Set group input/output ids for subgraph node
If we paste a subgraph node, clear the input connection map
Resync group node input/output node ids in the node instead of node manager, slightly slower but removes dependency on CAnimNodeManager::GetGroupNodeID