Galois conjugates for elements in extension of p-adics

[wuthrich]

It would be nice to have Galois conjugates for elements in finite extensions of Q_p.

E.g.

sage: R.<X> = Qp(3,20)[]
sage: K.<t> = Qp(3,20).extension(X^2-3)
sage: t.galois_conjugates()

should return [t,-t].

It is also not clear if the minimal polynomial of t is best over the field K, so x-t, rather than over the base field Q_p, i.e. x^2-3.