Allow the user not to close parens, quotes etc. about epsilon

[Zezombye]

Also maybe add autocompletion support for commas. For example, if I select "sum" from the toolbox, it gives me sum(|,,), and if I type '6' then ',', it should override the present comma instead of adding another.

The Casio calculators also support missing closing brackets btw.

[yeKcim]

A pretty solution, could be colored brackets.

If there is only one brackets level, stay black. Each sublevel has its own color. If a bracket is open and not closed (or closed and not opened) it's red. Colors have to be used each time it's helpful…

A mockup (I thought "1st level stay black" after drawing)

[matheod]

I think it is better if student are forced to close bracket.
We already have too many student typing 1+x/2 instead of (1+x)/2 ...

If this sort of thing get ever added, I think it should be an option disabled by defaut.

But some coloring of bracket could be good (for exemple cooloring the "cursor touched" bracked couple).

[RubenNumworks]

Related to #587

[RedGl0w]

Indeed, other application of this would be useful :
When you want to have an expression at numerator, but you didn't opened any parentheses at the beginning, just pressing a closing parenthese and then division would be nice (so allowing student not to open parenthese too)

[artaxxx]

Fixed in version 20