Add Constraint prior

bilby/core/prior.py

bilby/core/result.py

bilby/core/sampler/base_sampler.py

bilby/core/sampler/pymc3.py

bilby/gw/conversion.py

bilby/gw/prior.py

bilby/gw/prior_files/GW150914.prior

bilby/gw/prior_files/aligned_spin_binary_black_holes.prior

bilby/gw/prior_files/binary_black_holes.prior

bilby/gw/prior_files/binary_neutron_stars.prior

bilby/gw/source.py

examples/injection_examples/roq_example.py

test/gw_likelihood_test.py

test/gw_prior_test.py

test/gw_source_test.py

test/prior_files/binary_black_holes.prior

test/prior_files/binary_neutron_stars.prior

test/prior_test.py