Color preference for Sch editor and Waveform viewer

@physicboy @KSKelvin

OK, here’s a first pass at a tool to save/restore QSpice color settings. Look for QColorPrefs in the WIP folder on the dev branch:

I’m thinking that I should add a switch to restore only waveform color settings. As is, all waveform & schematic color settings are saved/restored.

Let me know what you think.

–robert