Reduce latency between captures.

This attempts to reduce latency between successive captures.

I noticed that often a couple guider iterations were required that were unnecessary, especially when dithering. This reduces that in a couple ways:

• If using the internal guider and OnePulseDither, there should not be any requirement for guide images, however two were required in the code. This eliminates that.
• The check for excessive guide deviation at the start of a capture is implemented in two redundant places. Removing the one inside SequenceJobState removes waited for a guider iteration before resuming a sequence. The check still works, as CaptureModuleState checks for a low-enough guide deviation as the first received guide drift in a capture and may abort/re-start the capture if need be.