use J2000 names

[paulthebaker]

Currently the pulsar list uses B-names as the primary name field where available and J-names as the alias. However, the IPTA data releases use the pulsar J-names as the naming convention (see, e.g., DR2 on gitlab). Since this is an IPTA resource, I think it should follow the conventions of the IPTA data releases.

A few other pulsars have multiple J-name aliases. If the B-named pulsars are changed, these should be double checked so their primary names match the names that will be used in IPTA DR3.

[dlakaplan]

This is fine if it's the IPTA policy. I don't think this requires a change to the code, just the database contents.