Slimmed down node and subclasses

Got rid of connection (that’s more a property between pairs of nodes),
and figure out type automagically.
Wire writing data reorganization

Keeping a bunch of data easily accessible is each Wiring::Node subclass
object.
Nodes array/index moved to node class

The array gets assigned to a class variable in Node and then the
indexer is calculated. This way the main code is a bit nicer and we can
just calculate everything in method calls.
Stub code for wiring