Allow alignment from plate solving

[kbahey]

This adds Alignment using Plate Solving to OnStep. For example, it allows the use of Mount Model tool in KStars/Ekos.

The work flow is to start an Align in OnStep with N stars (e.g. from the INDI control panel), then use the Mount Model with that same exact number of stars, and let Ekos turn the mount around the sky and take images, plate solve them, and sync on the coordinates.

When a sync is done (i.e. :CM# command) and OnStep detects that the alignment is in progress (i.e. number of stars aligned is not the same as number of stars selected), OnStep internally calls the AddStar align, mimicking an explicit :A+# command.

No error checking yet.

This is tested indoors, but still untested under the stars, please test if you can.

[kbahey]

This is now tested indoors, with KStars/Ekos/INDI, and works as planned.

Overview of the workflow can be found here.

[kbahey]

Howard,

Another person tested this with KStars. He had unrelated issues, but the OnStep part worked as intended (:CM# advanced the star align to the next star).

So this can go in to Alpha.