Add support for more general boundary constraints

[Al-Kindi-0]

As it currently stands, the most general type of boundary constraints are of the form $\frac{f(X) - b(X)}{Z(X)}$ where

1. $f(X)$ is the trace column polynomial,
2. $b(X)$ is a polynomial specifying the boundary values enforced on the aforementioned column,
3. $Z(X)$ is a zerofier polynomial on the enforcement domain associated to the boundary constraint

However, there are situations where we want to have boundary constraints which involve more than just one trace columns polynomial, say $f_0(X)$ and $f_1(X)$ and a constraint like $\frac{f_0(X) \cdot f_1(X) - 1}{X - g^{-1}}$ where $g$ is the trace domain generator.

I thought about this a bit and it seems to me that one solution could be to treat these constraints as transitional constraints. For this we will need to handle transitional constraints with multiple divisiors which should not be too involved, I hope.
The other solution of generalizing boundary constraints to handle such general constraints seems to be more involved than the first solution.