First run of SV secondaries with real target files.

[geordie666]

This PR updates the secondary code based on a first full-scale run of secondary targets for SV. It includes:

• Some general optimization, updating and debugging of the secondary code.
• Matching to the input sweeps files, not just to the actual targets, to find and populate primary TARGETIDs.
• Add the initial full bitmask for the sv1 secondary target files.
• Updates to the data model for the secondary targets to better reflect the data model of the primary targets.

[geordie666]

This PR now also adds outside-of-the-footprint, Gaia-only standard stars to the MWS masks for SV and the Main Survey. The new classes are:

• GAIA_STD_FAINT
• GAIA_STD_BRIGHT
• GAIA_STD_WD

the selections for these bits use a combination of existing code to implement:

• For GAIA_STD_WD:

  • The Main Survey STD_WD class for GAIA_STD_WD, just without matching to the Legacy Surveys.

• For GAIA_STD_FAINT and GAIA_STD_BRIGHT:

  • Our standard point source cut on Gaia Astrometric Excess Noise.
  • Our Gaia quality cuts for standards.
  • An isolation criterion preventing any standard from being closer than 3.5" to another Gaia source that is within 5 mags of brightness, borrowed from the STD_DITHER_GAIA cmx class.
  • Color cuts supplied by Arjun Dey that mimic our inside-of-the-footprint selections for STD_FAINT and STD_BRIGHT (which rely on Legacy Surveys fluxes).