Improvements to tutorial on dipole sources in cylindrical coordinates

[oskooi]

Two main improvements to the recent Tutorial/Nonaxisymmetric Dipole Sources:

1. Mention that for simulation of a dipole at $r = 0$, only a single $\hat{r}$-polarized point source is necessary rather than a combination of $\hat{r}$ and $\hat{\phi}$ sources as would be expected theoretically. See also #2452 (comment).
2. In the simulation script, rather than perform $M$ simulations where $M$ is determined analytically as $kr$, perform as many simulations as necessary until the radiated flux has decreased by some threshold relative to its maximum value. This modification improves the convergence of the results since internal testing has revealed that using a predetermined $M$ may truncate the expansion too early and therefore produce inaccurate results.

Also includes some minor fixes and improvements to the rest of the text and script.

[codecov-commenter]

Codecov Report

Merging #2483 (3832e84) into master (845cdf4) will increase coverage by 0.57%.
The diff coverage is n/a.

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@@            Coverage Diff             @@
##           master    #2483      +/-   ##
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+ Coverage   73.25%   73.82%   +0.57%     
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  Files          17       17              
  Lines        5212     5269      +57     
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+ Hits         3818     3890      +72     
+ Misses       1394     1379      -15     

see 1 file with indirect coverage changes