Singular.jl 0.4.5 released

Here is an overview of the changes in this release of Singular.jl:

• Singular.jl should no longer crash on the new rings that Singular and its libraries can create, or at least it should crash in far fewer cases. At a lower level, this means that we have the internal function create_ring_from_singular_ring for turning a libSingular.ring_ptr into a bona fide Ring.
• Singular’s algebraic extensions of QQ and Fp can now be constructed via the function AlgebraicFieldExtension. This function takes a univariate FunctionField and a minimal polynomial in the function field to create the algebraic extension.
• Various small bugs have been fixed.