Excise ERFA

[helgee]

Replace the calls to ERFA by pure Julia functions:

• [x] eraD2dtf
• [X] ~eraDat~ #31
• [X] ~eraDtdb~ #14
• [X] ~eraDtf2d~ #36
• [X] ~eraTaitt~ #4
• [X] ~eraTaiut1~ #8
• [X] ~eraTaiutc~ ~#13~ #39
• [X] ~eraTcbtdb~ #25
• [X] ~eraTcgtt~ #9
• [X] ~eraTdbtcb~ #24
• [X] ~eraTdbtt~ #14
• [X] ~eraTttai~ #6
• [X] ~eraTttcg~ #10
• [X] ~eraTttdb~ #20
• [X] ~eraTtut1~ #21
• [X] ~eraUt1tai~ #7
• [X] ~eraUt1tt~ #22
• [x] ~eraUt1utc~ #40
• [X] ~eraUtctai~ ~#15~ #37
• [X] ~eraUtcut1~ #38

[giordano]

In AstroLib.jl there are some functions for time conversion, but I don't know whether they can be useful here.

[helgee]

ERFA is officially excised 🎉 Congrats @prakharcode

[prakharcode]

Thank you @helgee could not have been possible without your and @giordano's support!