A means for question authors to change how operators are interpreted and displayed

[christianp]

This is related to #677, which is about parsing.
This is also loosely related to #939, which is about limiting which functions and operators are available in mathematical expression parts.

Question authors can change how constants are displayed, using the "custom constants" tab.

There are different conventions for how some operators are interpreted and rendered. The example that's motivating this issue at the moment is that somebody wants the boolean or operator to be displayed in LaTeX with the symbol +, and xor with \oplus, ⊕. At the moment, or is always rendered with \vee, ∨.

Could we have a table of LaTeX representations of functions and operators, to allow the author to give a different representation?

For consistency, the author should be able to say that the symbol + is interpreted as identical to or, so the student can write either a + b or a or b.