Bad column fibermask

[julienguy]

• Use fibermask bits BADAMPB, BADAMPR, BADAMPZ to flag fibers affected by bad CCD columns instead of using the fibermask bit BADCOLUMN that does not specify the CCD.
• This avoid having coaddition masked whole spectra when only one camera is affected.
• Code tested on tile 273 SP5. One Lya quasar that was fully masked in f5 run is now successfully fitted with redrock.

This addresses issue #1604 .

[coveralls]

Coverage decreased (-0.006%) to 25.192% when pulling a03ba2d on bad-column-fibermask into 0d7e5c0 on master.

[sbailey]

I confirm that for this tile petal, the only targets with significant changes were previously COADD_FIBERSTATUS=BADCOLUMN and are now COADD_FIBERSTATUS=BADAMPR or BADAMPZ, with 1/3 of the spectrum masked instead of all of the spectrum masked, at least making it possible for redrock to fit a redshift.

However, I think we should consider also setting a redrock ZWARN bit (perhaps LITTLE_COVERAGE?) for these cases, since they are fundamentally different from normal 3-camera data in that there are large ranges of redshifts for which we couldn't correctly fit an ELG. This is similar to how we propagate fiberstatus POORPOSITION and BADPOSITION into zwarn POORDATA and NODATA instead of requiring end-users to inspect both masks. That's a change on the redrock side, to be coordinated with this PR.