Add analytics, reorg front end code

[rwblair]

Lot of things got moved around. Need to test some more to be certain everything actually works as expected.

[codecov-io]

Codecov Report

Merging #616 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #616   +/-   ##
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  Coverage   70.79%   70.79%           
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  Files          56       56           
  Lines        2164     2164           
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  Hits         1532     1532           
  Misses        632      632

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[rwblair]

@adelavega Heads up I was running into performance issues with the react debugger running in firefox with large numbers of predictors. Let me know if you notice any other wonky performance issues.

Also need to add a 'ga_key': 'UA-whatvever' to the config.ts for analytics to work. I've been seeing my computer come up in the dashboard when using the sites.

[rwblair]

Spent some time this morning profiling the site, the slowness with selecting/unselecting elements on a long list of predictors can't really be avoided. It does re render each line in the table, which only takes a few ms per row, but at a max of 200 rows it adds up.

Not for this PR, but what do we think about putting each category of predictor into its own table that starts out collapsed?

[rwblair]

fixes #612 #610 and #569