Allow using different Gröbner basis backends

[behackl]

... like, for example, msolve.

[turnip314]

Hi @behackl, I have a PR for using msolve to compute the Grobner basis:
#7

This branch has the above changes as well as the option to compute general terms in the asymptotic expansion, and gives support for algebraic directions r:
#9

[behackl]

This is very cool @turnip314! I have this on my radar, but likely won't manage to properly review and test it before 1st week of March.

Are these recent PRs tied to some deadline?

[turnip314]

@behackl No deadline (as of now)! Just starting my Masters an refamiliarizing myself with the code.