spec pipeline file/dir naming cleanup

[sbailey]

This PR provides some file and directory naming cleanup:

• remove colons from spectro pipeline output directory and file names since they are a special character for Unix.
  • old: run/scripts/redshift_20180328-00:28:04/run_20180328-00:28:04.log
  • new: run/scripts/redshift_20180328-002804/run_20180328-002804.log
  • the new scheme is admitted less obviously readable as a time, but easier to work with when cutting and pasting and browsing directories with tab completion.
• use desispec.io.findfile() to get correct redrock hdf5 output file name

Additional features that came along for the ride while debugging the above:

• Fixed "fail" vs. "failed" typos in pipeline state tracking
• Added a --skip-psf option to desispec.test.integration_test for testing without spexec installed

[julienguy]

tested

[julienguy]

Stephen, why did you remove the backward compatibility of PSF I/O in traceshifts.py .
I would rather keep it for now because we have EM spectrograph PSFs in the old format on disk.

[sbailey]

It did not have backwards compatibility (it assumed only X/YTRACE and didn't look for X/YCOEFF). I tried adding it, which sort of worked, but resulted in extractions that has resolution matrices normalized to ~0.5 instead of ~1.0, thus eventually causing redshift fitting to fail due to masking. Rather than go further down that rabbit hole, I backed out my changes so I wouldn't leave messy if/then code that was only a partial solution anyway. i.e. there is a commit message about undoing changes for old PSFs, but in the end this PR doesn't impact any previous PSF format functionality (working or otherwise).

[julienguy]

ok. thanks for the clarification. merging.