rewrite a present "bitmex importer" for Gekko (nodeJS)

- A present „Bitmex importer“ for Gekko has to get rewritten, so, that it does not use anymore “GET /trade”, but rather than “GET /trade/bucketed” in order to speed up. - In case of unexpected errors the importer should retry for at least few min before it gives up - Every it needs to be commented - Deadline one day