Fix jrenderpgsql build errors

[oobayly]

A previous commit - ​https://github.com/JOSM/josm-plugins/commit/edd4b35b37f324f49f2a39a15cb1f5a3aff441e7 - changed the signature of S57osm.OSMmap to only accept a File object. This has made it pretty inflexible as we now have to pass a physical file.

The jrenderpgsql package generates OSM XML from a Postgres Query in-memory, and therefore is no longer able use pass the data to the OSMmap method.

I suggest overloading the S57osm.OSMmap method to make it more flexible by allowing it to accept InputStream and Document objects as well.

The reason for the Document overload is that at the moment jrenderpgsql generates hand written XML, which isn't ideal. It would be better that it instead creates an Document directly and pass it to S57osm.OSMmap without the overhead of it having to be parsed.

I've attached a diff of my changes and would welcome any comments.