This will be used as an IR of sorts to eliminate the XML, which will be far
too verbose to use in proofs. It also allows us to attach behavior to the
operator, which will end up defining two values for @as and @yields.

The previously-existing notation for this has been removed. These will be
updated soon to account for vectors and matrices, but until then, this is
simply nonsense.

This is an unnecessary feature to maintain right now. I will include
symbols at the very beginning of the index, which is common in mathematics
texts, and may will add a table of common symbols in the future.

Stacking originally seemed like a good idea, but perhaps this does read a
bit better (and looks more like the composition operation being applied),
and composes a bit better if we needed e.g. \bicomp\bicomp{R}.
It's also less ambiguous when it's over a larger expression. For example,
\bicomp{[A]} places \circ over top of the A, which looks as if it's
[\bicomp{A}]. It's obvious what the intention is in that context, since
\bicomp{A} makes no sense, but there could be other situations where it
doesn't. With this change, it results in {[A]}^\circ.

There's a lot of change that's likely going to take place with this thing,
but it's a start. The abstract summarizes the purpose of this---to formally
define TAME in terms of algebra, first-order logic, and [ZFC] set theory.
This came about while working on compiler changes and optimizations, since
it's difficult to ensure correctness (and discover further optimizations)
without being able to formally define the language. The focus at the moment
is the classification system rewrite, which can be expressed in terms of
first order logic and set theory.
This commit contains essentially a POC with some carefully chosen
mathematical foundations (abstractions of which are subject to change) and a
basic representation of a subset of the classification system for scalars.