Add `port` parameter to --wp

[mvexel]

This PR adds a port parameter to set the port the PostgreSQL database is running at so you can do

osmosis --rb planet/utah-latest.osm.pbf --wp database=osm port=5433 user=osm

This is convenient if you have multiple PostgreSQL instances running side by side or you are running the PostgreSQL server on some non-standard port for other reasons.

I did try host=localhost:5433 but that didn't work and also didn't seem like a very clean solution given that psql for example uses a separate parameter for it as well.