SF-3855 Stop logged in pages reappearing via the Back button after logout

[Nateowami]

Fixes a bug where you can log out, then click back and see the entire page you just logged out of.

The bug was caused by a "feature" in Chromium where the bfcache ("back forward cache") stores the state of the page so when the user clicks the back button navigation is instant. They don't make it trivial to opt out of, but if you set Cache-Control: no-store on the html file you're serving, and meet other criteria, it disables the cache.

I'm not sure if the problem was active in Firefox, but if it was this should fix it there I think. This fix is mostly targeted at Chromium, and I don't currently know of a fix for Safari or if there is one.

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This change is 

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.30%. Comparing base (5767261) to head (0de91ae).
⚠️ Report is 8 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/SIL.XForge.Scripture/Startup.cs	88.88%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4081   +/-   ##
=======================================
  Coverage   81.30%   81.30%           
=======================================
  Files         670      670           
  Lines       43462    43480   +18     
  Branches     7105     7134   +29     
=======================================
+ Hits        35336    35352   +16     
- Misses       6951     6952    +1     
- Partials     1175     1176    +1     

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[pmachapman]

I was able to test this locally using the Docker container, and via Chrome Dev Tools' bf cache cheker I could confirm that the Back/Forward cache was disabled by your PR.

@pmachapman reviewed 2 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Nateowami).