tailor AsciiMath better for MathObjects

[Alex-Jordan]

This makes changes to the AsciiMath portion of the MathJax config so that it behaves more consistently with MathObjects. AsciiMath input is used by MathView and can be used when composing text that can have math that will be rendered (a student's essay answer or instructor feedback). Changes are:

• disable in, so you don't see a ∈ on your way to making ∞.
• disable ne so you can enter dne and none without seeing d≠ and no≠.
• as has been the case for a long time, let ** be interpreted as ^.
• replace AsciiMath's infty with inf.
• add Re, Im, log10, U, and ><.

This is well on its way to addressing #638. Perhaps more can be done to get greater consistency with MathObjects and AsciiMath input, but the process is demonstrated now for removing, modifying, or adding triggers.

[Alex-Jordan]

I made some changes to this.

• more concise code (and I think more efficient, but that depends on efficiency of javascript looping and indexOf method)
• In addition to adding what I added before, also added infinity, Infinity, Inf, INFINITY, INF, none, None, NONE, dne, Dne, DNE.
• No longer disabling in. If you type in, you see ∈. But as soon as you type an f the underlying text is inf and now you see ∞. I think this is fine, and allows in to still be there in case (for example) an instructor wants that in some feedback message.
• No longer disabling ne, since none and dne are now officially recognized.

[Alex-Jordan]

I updated the var declarations I added (but not the ones that were already in the file and not part of this change).

I'm not sure how best to change the formatting on newTriggers. Is the prettier change coming soon?

[drgrice1]

Don't worry about the prettier formatting. That will be taken care of when it is ready. I just wanted to point out that the wide formatting wont work with that. Like perltidy, prettier will auto format the code.

[pstaabp]

Should we close #638 now?