Documentation update to omni_sample_dpdf

Update documentation in subroutines/omni_sample_dpdf.pro to explain that
this routine is not limited to use with DPDFs, but may be applied to any
pdf for which random samplings are desired.  Otherwise, some minor code
cleanup and potential bug fixes.
Add Reid et al. (2014) parallax table

Add MRT from Reid et al. (2014, ApJ, 783, 130) containing trigonometric
parallaxes to masers in HMSFRs.  This replaces the MRT created from the arXiv
preprint LaTeXZ submission file.
Merge branch 'master' into release

Keep the 'release' branch up to date with the master.  The 'release' branch
will eventually diverge when components of tracked files are removed as
unnecessary for release, such as the mass-deriv configuration calls in
omni_read_conffile.pro.
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).