Add ability to load additional waveforms for the waveform viewer

[PetePupalaikis]

This could be done with a "load additional waveform" from the waveform viewer dialog.
Or (or in addition), I can add a waveform component to the schematic (just for viewing).
Also, I can add all source waveforms to the viewer possibilities.

This feature should be worked on in conjunction with methods to turn on and off waveforms.

Also, in the simulator or virtual probe, I might want to have a preference to process all waveforms all the time, and then one could simply turn them on and off. The waveform could be named simply by the device and port of the device.

[yanbinc]

So is it possible to read latest tr0 file?

[PetePupalaikis]

@yanbinc This issue is more related to the fact that when simulation completes, all waveforms that are probed in the schematic are shown in the simulation, and that there is no other way to add waveforms to the view (like to compare them). The reality is that the entire waveform handling needs to be improved.

the improvement would be to:

• turn on and off waveforms in the view.
• add other waveforms to the view (either from other projects or from files).
• to be able to delay, offset, or otherwise adjust waveforms in the view.

The reading of spice files or other file formats relates to #5.