add id function

[felixroos]

to tag a node with an id. on update, all new nodes that have a matching id in the set of old nodes, we don't create a new node, but instead only copy over the reference. this will preserve state. it will also be very helpful when a ui is used that has ids for nodes for example.

impulse(4).seq(100,200,300).id('myseq').sine().out()

maybe ids can also tag all nodes that came before, dfs style?

impulse(4).seq(100,200,300).sine().id('myseq').out()

it will also be very useful for delay lines, to preserve the buffer (which is currently solved manually, just for delay)