Implement caching of SVO filters

[cgarling]

Implements caching of filters queried from SVO. Includes an update_filters() function that will redownload all cached filters from SVO, effectively refreshing the cache.

@lucasvalenzuela how does this look?

[codecov]

Codecov Report

❌ Patch coverage is 68.88889% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.10%. Comparing base (21e9344) to head (32f8001).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/svo.jl	71.42%	12 Missing ⚠️
src/plots.jl	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #33      +/-   ##
==========================================
- Coverage   80.60%   80.10%   -0.51%     
==========================================
  Files           6        6              
  Lines         366      397      +31     
==========================================
+ Hits          295      318      +23     
- Misses         71       79       +8     

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[lucasvalenzuela]

I would save these as .xml files instead

[lucasvalenzuela]

It works really well and looks good to me! I have added one comment in the review (xml vs. txt files) and also added a PR adding clear_filters to remove all filters in the cache: cgarling#7

One thing one could still add is a keyword argument to get_filter that forces the downloading of the file, and/or a keyword argument that prevents the caching of the downloaded file. And one could equivalently add an argument to clear_filters or a new clear_filter to remove one single specified filter. But maybe that is too much of an edge case.

[cgarling]

Couple updates:

• cached_filters returns a list of the filters currently in the cache
• update_filter("2MASS/2MASS.J", :Vega) can be used to update one specific filter in the cache. Calling update_filter() updates all of them.
• clear_filter("2MASS/2MASS.J", :Vega) can be used to delete one specific filter from the cache. Calling clear_filter() deletes all filters from the cache.

With these features complete I think we should be good to merge this and register the package. What do you think @lucasvalenzuela ?

[lucasvalenzuela]

Everything works beautifully! For the docstrings I noticed you put in two method documentations in the same triple quotation marks block - does that actually work? I am used to seeing separate docstrings for each method.

Apart from that I think this is ready to go and be registered.

[cgarling]

It does work but it's kind of a bad habit, I think it's better form to have multiple docstrings so I changed that now.

Thanks for all your help! I'll merge this and try and register the package when I get a chance. You think we should register at 1.0?

[lucasvalenzuela]

I saw you already bumped it to 1.0 - in any case I don't have any preference on 1.0 or 0.1. Fantastic to see this getting this registered soon, thanks for all your work on this package!