Remove importing of fixtures as part of the "steering initialize"

From now on radio admins are able to customize fixtures with the provided commands "fixtures-create" and "fixtures-import" (compare docs).

changed milestone to %1.0-alpha3 — Playful Platypus

added P1 + 1 deleted label

assigned to @eigenwijsje

added Doing label

closed with commit f65a9709

removed Doing label