Clean up GET and POST usage in article-level AJAX requests

[davidskalinder]

See #101. This issue is just for the article-level AJAX so that it can be PR'd separately.

From #101:

Strategy:

1. grep for GET
2. Start at first JS file
3. Search for first GET and change it
4. Search for other calls to same URI and change those too
5. Search for URI in controller
6. Add , methods=['POST'] to @app.route() params for URI
7. Change all request.args.get('ting')s to request.form['ting']
8. grep for URI to confirm that it doesn't occur anywhere else important
9. Commit

Repeat until no more non-idempotent GETs are left.

Afterward, review commits to see what needs testing. If testers are up for it, might want to open a new issue for each URI (though that might be too much).

See https://github.com/davidskalinder/mpeds-coder/issues/101#issuecomment-658461660 for template of changes that will need testing.

[davidskalinder]

b4bd0ac8a72f merges the changes from #101 into an otherwise minimal article-enabled branch. That might be all I'll get to for a while, but the comments above are a nice list of next steps...

[davidskalinder]

Detailed list of changes:

_add_article_code

Sent from:

• selectArticleCheckbox JS
  • Triggered by filling a checkbox in the article-level block EDIT: DS tested 2020-09-02-1620

Description: Adds a new line to coder-article-annotation table, based on article, variable, input value, and text (for text capture, probably unused)

_del_article_code

Sent from:

• selectArticleCheckbox JS
  • Triggered by clearing a checkbox in the article-level block EDIT: DS tested 2020-09-02-1620

Description: Deletes a line from coder-article-annotation table, based on article, variable, and input value

_change_article_code

Sent from:

• storeArticleTextInput JS
  • Triggered by removing focus from any text or textarea control in article-level block EDIT: DS tested 2020-09-02-1621

Description: Changes (deletes and then adds) a line from the coder-article-annotation table, based on article, variable, and input value

[davidskalinder]

Merged change_article_gets_to_posts into testing: 7e71728574250

[davidskalinder]

No apparent problems with this after a week of testing with training articles.