Phasing memo 2.0

[kartographer]

Updates the phasing memo.

Description

Updates the phasing memo to document the "new" phasing framework within pyuvdata (primarily for UVData objects).

Motivation and Context

I was asked for documentation on phasing, and 3 years later I've finally finished it!

Types of changes

• Documentation change (documentation changes only)

Checklist:

• I have read the contribution guide.
• My code follows the code style of this project.

Documentation change checklist:

• Any updated docstrings use the numpy docstring format.
• If this is a significant change to the readme or other docs, I have checked that they are rendered properly on ReadTheDocs. (you may need help to get this branch to build on RTD, just ask!)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.93%. Comparing base (02baee4) to head (beb3c34).

Additional details and impacted files

@@              Coverage Diff              @@
##           prep_v3.0    #1442      +/-   ##
=============================================
- Coverage      99.93%   99.93%   -0.01%     
=============================================
  Files             41       40       -1     
  Lines          21138    21103      -35     
=============================================
- Hits           21124    21089      -35     
  Misses            14       14              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[bhazelton]

Why is the calfits memo pdf updated in this PR?

[kartographer]

@bhazelton -- I edited the calfits.tex file in #1437 but forgot to recompile. At issue I believe was the update for input_flag_array moving into v3.

[bhazelton]

This is great, thank you! Lots of little comments but generally I really like your updates, especially the primer on celestial coordinate systems -- super useful.

[kartographer]

Thanks @bhazelton! All little comments should now be addressed (along with one final check for misspellings which I apparently forgot to do on the last run).

[bhazelton]

Found a couple more minor things but I think we're close!

[bhazelton]

Looks good, thank you!!