Fix time axis for runs with negative times.
Fix parsing of negative declinations.
Simplify JD calculation.
Fix 0.184ms BJD time offset.
Increase precision of .ts timestamps.
Replace Stumpf BJD conversion with sofa.
Remove precession calculation and require J2000 RA/Dec.

The barycenter calculation returns coordinates aligned
with J2000, so the RA, Dec used to calculate the BJD
light-travel time must also be in a J2000 equivalent
epoch.
Use 80-bit extended precision for bjd times.