Resolve "Copy nodes from host to interpreter"

Closes #40 (closed)

To do:

• Copy nodes lazily (add a coerce node to the interpreter like on the host, i.e. #41 (closed))
• Copy any kind of node, not just integers
• Let this work with nodes which have received some arguments in the interpreter already
• Let this work with garbage collection: don't clean up nodes on the host when they are referenced from the interpreter
• When copying to the interpreter, make sure there is enough space and else garbage collect first