Adding support for deriving the Node trait

[ostrosco]

• Added the ability to implement the Node trait via a derive procedural macro. This provides a much cleaner syntax for creating new nodes.
• Added two helper types: NodeReceiver and NodeSender. These types must be used when creating the structure for the Node derive macro to know which fields are crossbeam senders and receivers.
• Nodes derives via the macro must have a run() function implemented on the structure which is used on each iteration of the node. This will be a compile-time error if it is missing.
• Updated all nodes to use the new implementation.
• Remove the create_node! macro and its support functions.