Add in dithering functionality into AORP

[dsand]

Many users will want to perform small dithers in between exposures to help with bad pixel rejection. Lets implement this functionality in AORP, and then also in our commands to RTS2. I am not sure at all how to do the RTS2 part.

This issue will track progress both for implementing dither requests in AORP, and for executing them in the queue.

[dsand]

I took a quick look at how Las Cumbres implements dithering (they call it mosaicing) on their web interface. There is some documentation here. This seems needlessly complex.

Here is some documentation on the dither patterns offered by HST and the ACS camera.

[dsand]

I will think about this some more, but I think we should give a couple of simple options:

1. A random dither, with a 'largest offset' constraint. So the dithers would be random in X, Y but the biggest dither would be a specified value A (like 30 arcsec or something, user specified).
2. A box dither, possibly with an orientation/angle offset. The pattern will repeat after all the vertices of the box have been observed.

[pndaly]

At some point, I should demonstrate NGUI to you. This was the NEWFIRM gui that allowed observers to choose dithers, maps and several dither patterns (RA-walk, Dec-Walk, Random-Walk, RA-Dec-Serpentine, 5-point, Chip-Center to name a few). I'm not suggesting we use that code but the algorithms for producing the individual observation offsets are correct.

[dsand]

EXCELLENT.