switch from osmosis to pyosmium for updates

Pyosmium comes with convenient functions for finding the
right state and does not require external files for
rembering the state. Updates can now conveniently
set up by simply running ./utils/update.php --init-updates
and state is kept directly in the import_status table.

This change requires an update in the database schema.
Run the following to update:

ALTER TABLE import_status ADD COLUMN sequence_id integer;
ALTER TABLE import_status ADD COLUMN indexed boolean;
ALTER TABLE import_osmosis_log ADD COLUMN batchseq integer;

sql/tables.sql

@@ -1,12 +1,15 @@
 drop table if exists import_status;
 CREATE TABLE import_status (
-  lastimportdate timestamp NOT NULL
+  lastimportdate timestamp NOT NULL,
+  sequence_id integer,
+  indexed boolean
   );
 GRANT SELECT ON import_status TO "{www-user}" ;
 
 drop table if exists import_osmosis_log;
 CREATE TABLE import_osmosis_log (
   batchend timestamp,
+  batchseq integer,
   batchsize integer,
   starttime timestamp,
   endtime timestamp,