Named `FormulaEquationInput` (name up for debate)

- Based off ChemEqnIn
- Add FormulaEquationInput in inputtypes.py
- Add a call to a skeleton method for a preview

javascript:

- Queue up some MathJax
- Put some ordering on the AJAX requests: add a parameter when the request was started, when it returns check that it isn't outdated before displaying the preview
- Tests

Note: we moved the `jsinput` tests and DISABLED them, because they were causing the tests to fail.

Updates comment
Make Model descriptor class property.
Fix tests

Refactors trigger function.
Fixes Ui bugs: captions.
Fixes bug with Youtube on page load.
Hotfixes html5 video streaming bug.
Adds test video files to the project.

Not sure why these had capital-I's in them, since the text just above shows lowercase-i's, and uppercase doesn't work properly.

A few places we used an option of 'imaginaryi', which isn't a real option.  Doesn't change any behavior.

import path not consistent with dev machines?)

import path not consistent with dev machines?)

import path not consistent with dev machines?)