[Feature Request] Add probing of simulated circuit

[madscientist159]

Currently evaluating QUCS as an alternative to LTSpice. The one thing that is standing out as a blocker is that a simulated circuit cannot be dynamically probed -- all probe points have to be defined in advance, involving constantly editing the schematic and re-simulating. For large circuits this is a non-starter -- even for SMPS work (our intended use case) accurate simulation can take tens of minutes, and we need to be able to probe the resultant circuit to find instability etc. after the simulation has completed.

This could logically be broken down into two tasks:
1.) Simulate all nodes and expose these nodes in the node list in the graphing tool (e.g. AUTO.R1.node1.V)
2.) Allow point+click selection of the nodes and auto-add to graphing tool

[in3otd]

dynamically probing the circuit would of course be a nice feature. Interestingly, for the transient simulations, already all the circuit nodes voltages are saved in the simulation results, but the Diagram variables selection dialog hides the ones where the user did not assign a name in the schematic. It should not be too difficult to include all the nodes in the simulation results list and show on the schematic the names automatically assigned to every net not explicitly named.