OCSADV-29: Improved AGS warnings / errors and fixed bug about no guiding feedback update when positions modified in Target Editor.

OCSADV-170 OCSADV-172 OCSADV-175: Updated error messages and fixed bug where guiding feedback wasn't being updated when RA and Dec were changed through TargetEnvironment editor text fields.
Un detallito.  A more idiomatic way to write that might be: `val saturated = saturationLimit.exists(_.getBrightness > mag.getBrightness)`