Merge custom nodes implementations

Conflicts between two implementations were resolved. Server-independent implementation was used as the base. Command to send custom nodes to Dynamo server was added. I'll provide more comments inline.
There are no reasons to keep both, guid property is needed for Dynamo server only, but it fully duplicates functionId;
We have to ways to resolve this: 
1) Remove functionId and use guid property instead
2) Remove guid property and add this to the serialization pipeline, when object transforms for sending to Dynamo;