Add a --quiet option to osm2pgsql to run quietly

I have added a simple -q/--quiet option to osm2pgsql which, if given, will not print anything to the terminal while running.

Often osm2pgsql is used in a crontab to regularly keep a database up-to-date with OSM data. However cron will send an email if there is any output, meaning anytime you use osm2pgsql, you'll get a big long email with lots of data. This noise can hide important signal. Having a way to turn this output off is very benefitial in this case.

I am using this fork daily for several weeks myself now. I have only done this for the simple import into postgis now.