Fba launch io

[araichoor]

This PR is a major refactoring of the fba_launch, with factoring out all the functions to a new utility script fiberassign.fba_launch_io.

Though, there is no change on the produced files, except for the following minor bugs corrected in the process:

• ToO original file column values were not propagated in fiberassign-TILEID.fits.gz; this led to zeros in ToO rows in fiberassign-TILEID.fits, noticely the SV3_*_TARGET; now this is corrected; this changes the reported stats in the QA plot and the log;
• it was always reported in the header that the proper-motion correction was applied, irrespective of args.pmcorr="y" or "n"; now it is reported only if arg.pmcorr=="y";

Further minor changes:

• addition of a FASCRIPT keyword in fiberassign-TILEID.fits.gz, to keep track of which script was used to generate the tile; it will be fba_launch for the main survey, but dedicated scripts for dedicated tiles.
• now using desitarget.geomask.match instead of customed defined unq_searchsorted
• replacing get_isaen by desitarget.gaiamatch.gaia_psflike, to enforce consistency (e.g., if AEN cuts for Gaia/EDR3)
• changing the colorbar range for fiber assignment in the QA plot.
• removing divide by zeros in flux to magnitude conversion.
• correctly formatting the sbprof allowed choices

I have checked I can reproduce the output products (modulo the small differences due to the aforementioned bug correction):

• a run from the desi master environment
• one already designed tile (TILEID=36).

[araichoor]

I was wondering if some special actions are needed to get the following github feature: when clicking on a function name, it opens a box with a link to where the function exists.
I notice that this is not active in my branch for fba_launch_io.py.

[araichoor]

I just pushed two commits, making fba_launch_io.create_gfa() a bit more general, with renaming it create_target_nomtl().
and totally unrelated (sorry): also allowing SV1 in make_qa.

[araichoor]

and a commit to enable args.survey=main or sv1 in fba_launch.
I added "for free" sv1, as it ll be required for some dedicated tiles (e.g. those of today).
as there is no main-mtl file, I couldn t test it actually, but sv3 should be blind to that change.