use knobs label instead of name

[Mitja Müller-Jend]

Regular user is used to refer to knobs by their label, not their name. However, to access the knob in python, we must use the name. Since each nodes may have a different knob name to label combination, we'll have to add a lookup to go from label to name for every node.

• knob list: do not store actual knob objects, only name and label.
• knob filter models: filter through every node