Documentation on monomial orderings

[thofma]

At some point in time, Dan introduced the following important piece of information in the documentation (important for people who not want to write slow code):

!!! note
    As the above functions take an arbitrary ordering, they are much slower than
    the versions from AbstractAlgebra, which use the natural ordering in the
    parent polynomial ring: `default_ordering(parent(f))` is not necessarily
    this natural ordering. If this ordering of the parent is desired, or if the
    ordering is not important, it is recommended to use the following.
    - `AbstractAlgebra.coefficients(f)`
    - `zip(AbstractAlgebra.coefficients(f), AbstractAlgebra.exponent_vectors(f))`
    - `AbstractAlgebra.exponent_vectors(f)`
    - `AbstractAlgebra.monomials(f)`
    - `AbstractAlgebra.terms(f)`
    - `AbstractAlgebra.leading_coefficient(f)`
    - `AbstractAlgebra.leading_exponent_vector(f)`
    - `AbstractAlgebra.leading_monomial(f)`
    - `AbstractAlgebra.leading_term(f)`

It appears that this was removed in #1760. @wdecker @ederc not sure if this was on purpose? If so, do you mind if we reintroduce it? Maybe in the developer documentation part?

[wdecker]

It appears that this was removed in #1760. @wdecker @ederc not sure if this was on purpose? If so, do you mind if we reintroduce it? Maybe in the developer documentation part?

I removed this since I found it very confusing for the average user, in particular since the wording is not accurate enough. On the other hand, it might indeed be important for developers. But not every developer will read the developer documentation part if he is just interested in monomial orderings. So how about adding something like !!! note for developers to !!! note, !!! warning, and friends so that informaton like the one considered here can be entered at the right spot.