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.
Clean out utils/ directory

Clean out utility routines not needed by the to-be-released distance-omnibus
code.
Upgrade to GPL V3

Upgraded the license to GPL V3 from V2.
Upgrade to GPL V3

Upgraded the license to GPL V3 from V2.
Merge pull request #1 from tbowers7/license

Upgrade to GPL V3
Merge branch 'master' of github.com:BGPS/distance-omnibus
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 'document'

Bring this branch back to the master -- only wanted the branch to test how
git handles such things.
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.