Output line

Output lines are nobs which have no natural counterpart in the human neural system. They are only tools for the construction of a model. When plugged into an input line, they turn into knots. Commands:
 * Output neurons can have several incoming dendrites, but no outgoing dendrite.
 * Output neurons without incoming dendrites can exist in a model, but they make only sense as a temporary state.
 * Add outgoing dendrite
 * Stop on trigger on/off
 * Delete
 * Select nob/Deselect nob