Resolve issues identified in !408

See merge request lscsoft/bilby!597

1) Make the constants consistent with those used in lal
2) Deprecate the gps_time_to_gmst function
3) Use the lal.GreenwichMeanSiderealTime(time) method directly

Unified calls to super class in __init__ methods

See merge request lscsoft/bilby!593

Fix missing default kwarg in cpnest

See merge request !591

Fixed issue with mutable default argument

See merge request lscsoft/bilby!596

Fix for MultivariateGaussianDist for 1d cases

See merge request lscsoft/bilby!587

make info message a debug

See merge request !588

    - fix sampling from a multi-variate Gaussian dist in the case that the distribution is only for one parameter

Fix reading of latex_labels in prior file to avoid multiple escape characters

See merge request !581

Fixup documentation

See merge request lscsoft/bilby!583

Deprecates some of the problematic helper functions

See merge request lscsoft/bilby!584

- The helper functions are not tested rigourously and hide detail under
  the hood. This deprecates them in favour of the users setting things
  up themselves.

Catch ValueError raise by dynesty resample_equal function

See merge request lscsoft/bilby!585

Fixing bug in dt

See merge request lscsoft/bilby!586

Adds the LAL version information to the meta data

See merge request lscsoft/bilby!580

Update sampler_requirements.txt: PyMC3 v3.7 is Python 3 compatible only, so change the requirements

See merge request lscsoft/bilby!582

Resolve "Improve validate filename"

Closes #403

See merge request lscsoft/bilby!577

Resolve "Emcee chains error"

Closes #398

See merge request lscsoft/bilby!579

Resolve "Nightly C.I. breaking"

Closes #404

See merge request lscsoft/bilby!578

Remove the sqrt(2) normalisation from the scalar longitudinal mode

See merge request lscsoft/bilby!574

In !573, the GW150914 prior was removed from the default directory. The
tests rely on this in order to run, this adds it back in.

This change allows psd files wihtout a "/" in their paths to be used. This will
also improve the logged output and increase the clarity of what is being
checked where.

replace removed scipy.interpolate.spline

See merge request lscsoft/bilby!576

Added try except clause for building the lookup table

See merge request lscsoft/bilby!575