Set up variables and question
Add hints
Accept both possible answers
Don't accept extraneous solutions
Convert two exercise types to one
New exercise type - identify extraneous solutions
Fix factoring
Add another possible answer to multiple choice question
Complex numbers captured by regex
Merge pull request #46263 from petercollingridge/add-sub-comp2

To address https://trello.com/card/adding-and-subtracting-complex-numbers-shouldn-t-accept-blank-answer/4d87e664967a0775082939ab/579

Test plan: Try exercise and make sure it accepts the right answer whichever way it is written 

Auditors: eater, alpert
Fix up most instance of \text{} using the linter

Summary:
There are a couple cases that had to be fixed up manually, and a lot of
instances that incorrectly tried to wrap $._ around things that shouldn't be
translated (mostly the chemistry exercises). There are a couple instances that
I wasn't sure about (like the "R" in remainder) that I didn't include.

Test Plan:
Visit the changed exercises, make sure that the exercise renders and
there were no errors. Take all the hints, and make sure that instances of text
in mathjax render correctly.

Reviewers: john

Reviewed By: john

CC: alpert, eater

Differential Revision: http://phabricator.khanacademy.org/D2445
Merge pull request #45862 from petercollingridge/extra-sol

Extraneous Solutions to Rational Equations
Add a ?nographie parameter to local mode to inhibit rendering graphies

Used for converting exercises to perseus items. Don't render so we can just scrape the code directly.

Test plan: add ?nographie to the url of an exercise in local mode and note that you get javascript, not pretty pictures

Auditors: alpert
Fix the auto-expand-hints logic

Summary:
People were complaining that hints were auto expanding in mastery mode.
While there might be a deeper fix to not do this at all in topic/mastery mode,
the logic is inverted anyways, so it only shows up in the most confusing
states right now.

Test Plan:
open some hints in /math/arithmetic/fractions/understanding_fractions/e/fractions_on_the_number_line_1
reload it, make sure they're auto expanded
reload it in athena as a task, make sure it's auto expanded

Reviewers: james, alpert

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D2468
Fix some unbalanced tags

Test Plan: Visit http://localhost:8083/exercises/extraneous_solutions.html and make sure problem/hints render correctly

Reviewers: eater

CC: alpert

Differential Revision: http://phabricator.khanacademy.org/D2480