Set fid plots to autoscale min y-axis values

This change autoscales the min y-axis values of the fid drift plots in
in 5 arcsec increments if the minimum plot value is less than the default
of -25 arcsec.
Exclude 4 obsids with bad data from the fid drift query

Instead of filtering the fetched data, this change rejects 4
observations in the initial database query.
Change fid drift plot symbol

This changes the symbol from a ',' to a '.' with size 4.
Merge pull request #1 from sot/autoscale_min

Autoscale the minimum values in the fid drift plots