polynomial: WIP on DerivativeBinomAt
var_degree_map: update comment
free-semiring: improve printing
polynomial: implement DerivativeBinomAt
newton: use VarDegreeMap for computing derivatives
matrix: improve move assignment and constructor
polynomial: add a few missing "const"
polynomial: update tests
newton: alternative solver without symbolic delta
monomial: delete unused method
float-semiring: whitespace only
float-semiring: move definitions to the header
Merge branch 'semilinear' of https://github.com/michalt/newton into michalt-semilinear

Conflicts:
	c/src/polynomials/polynomial.h