Added Docker setup for initial database import

This MR adds the import of an osm.pbf file into an empty database.

Related to https://git.gfz-potsdam.de/dynamicexposure/server-components/compositions/docker-openbuildingmap-import/-/merge_requests/2

\rfc @marius \approve @ds

files/openbuildingmap.style

-#
-# This file contains the mappping information for osm2pgsql
-# specific for the OpenBuildingMap.
-#
-# Please append this file to the empty.style provided directly with
-# the osm2pgsql code.
-#
-node,way  osm_timestamp	timestamp(0)	linear
-node,way  osm_version	int4	linear
-node,way  osm_uid	int4	linear
-#
-# setting this to "delete" prevents from the column gets created.
-node,way  osm_user	text	delete
-node,way  osm_changeset int4	linear