Add epsilon attribute to Specifier

[Breush]

Rationale is that from minpoly.h, we can find some switch based on certifyInconsistency, which should be replaced by a epsilon and do the switch when epsilon > 1 / fieldSize:

	template<class Polynomial, class Blackbox>
	Polynomial &minpoly (
			     Polynomial                       & P,
			     const Blackbox                   & A,
			     const RingCategories::ModularTag & tag,
			     const Method::Blackbox           & M)
	{
		if (M.certifyInconsistency) {
			// Will make a word size extension
			// when field size is too small
			minpoly(P, A, tag, Method::WiedemannExtension (M));
			return P;
		}
		else
			return minpoly(P, A, tag, Method::Wiedemann (M));
	}

See #53

[ClementPernet]

same happens in rank.inl