Adds additional LOOK Project support

• Allow editing of window for spectroscopic calibration targets.
• Fix for incorrect slot length calculation with multiple spectra exposures.
• Upgrades astropy minimum version to 3.2.3 for updated USNO Earth Orientation Parameter URLs and also the minimum version that works on python 3.8
• Adds storage of the orbit RMS from MPC DB
• LOOK Project updates:
  • Adds storage of reciprocal semi-major axis from MPC DB as a PhysicalParameter
  • Adds additional Body attribute to return reciprocal semi-major axis
  • Adds new get_cadence_info() method to summarize whether an object's cadence is underway or has halted and adds this into the LOOK Project template
• Allow search of static (sidereal) calibration sources.