Allow defining symbols that break out of exp

[JMSS-Unknown]

The given symbols or strings will break out of an exponential. For example, if you type 2^2 and then press =, the result will be 2^{2}= instead of 2^{2=} as before

The editor also removed trailing white space automatically, sorry about that.

[daniel3735928559]

It isn't clear to me that exponentials are special in this regard. For example, entering s i n ( x = 2 probably should also result in output sin(x) = 2.

I think what's actually going on is that some nodes/characters should be restricted to being children only of the top-level c node and when they are entered, they should always trigger breaking out of wherever they are back up to the top-level c-node and be placed there.

For example, in this PR, if I enter 2 ^ 2 ^ x = then I end up with 2^(2^x = )

[JMSS-Unknown]

I made it that some symbols like = can only be in the top most node as you said, but my main focus of this pull request was that if you type 2 ^ 3 + the output is {2}^{3}+. This is limited to superscripts and subscripts (which it now support)