Update to subroutines/omni_compute_ebars.pro

Update error-bar computation routine to gracefully handle bimodal PDFs computed
from Monte Carlo calculations of derived quantities.  Sometimes the secondary
peak (with ~15-20% of the probability) can have a taller peak in the PDF because
of binning considerations, but this peak is not the one we want to select as
the "Maximum-Likelihood" peak because the peak itself does not contain a
majority of the probability.  Updates to the routine check for bimodality, and
properly mask the PDF, if desired.
Make LINFIT_PLOT robust

Add option in utils/linfit_plot.pro to use an outlier-robust fit in the form
of the IDL-included LADFIT.  Also cleaned up the documentation, and added an
optional output of the fit values for use however the programmer sees fit.
Merge branch 'release'

Make sure everything on the 'release' branch is on MASTER (which it is, but I
wanted git to tell me) before making release-only changes to RELEASE.
Add flag for infinite linewidth in import

Modify create_local_files/omni_import_velocity.pro to kick a flag when fixing
the linewidth of a dense gas catalog entry (entry was infinite).  No substantive
change to routine except this and documentation, but the flag may be used
elsewhere when doing physics (i.e. linewidth relationships).
Merge branch 'master' into release

Merge latest version of the MASTER into the RELEASE branch.  This will be the
primary type of commit on this branch, with the exception of excisions from
repository routines of code sections dealing with mass or other stuff.