Add option to use guiding without commanding TCS

[chazshapiro]

Sounds dumb... but we only record image quality measurements while guiding. We want to see how these measurements change when not guiding. So we need an option to enter guide mode but without moving the TCS around. Ideally, we would just have the acquisition/guide loop always "succeed" (force it to think the result is OK and keep going) but never move the TCS. If for some reason the TCS commands during the acquisition phase are needed to get to guiding, that's fine.

I'm adding a priority tag but please adjust as needed.