Add observing statistics to AAVSO output file

[rzellem]

to help future-proof EXOTIC's output, let's also report things like the seeing and x/y centroid positions in the AAVSO output file- that would enable folks in the future to explore using additional detrend parameters (e.g., like detrending flux from the target's position on the focal plane)

[ivenzor]

About the seeing, in the output txt we upload to AAVSO I can see the the seeing rating in NOTES, e.g.:
#NOTES=**First image seeing 99 (0: poor, 100: excellent)**, Teltemp - Camtemp 15.0. These observations were conducted with MicroObservatory, a robotic telescope network managed by the Harvard-Smithsonian Center for Astrophysics on behalf of NASA's Universe of Learning. This work is supported by NASA under award number NNX16AC65A to the Space Telescope Science Institute.

About the x/y positions, I can see the x/y position of the comparison star, e.g.:
#COMP_STAR-XC={"ra": "131.479538019", "dec": "-7.9810051795", **"x": "401", "y": "276"**}

Should a similar line containing the x/y position of the analyzed star be present in the output file?