Update renderd.conf mapnik paths to default ubuntu paths with mapnik PPA

These are *more* more likely to be what a user has, so less likely to have to be changed
Make sure that renderd is started after postgresql in init script for debian

This will work even if postgresql is not installed, because dependency is a
soft one.
Merge pull request #60 from osm-fr/lsb

Make sure that renderd is started after postgresql in init script for debian
render_list was not blocking on requests and would swamp renderd with requests
Merge pull request #53 from pnorman/patch-2

Update renderd.conf mapnik paths to default ubuntu paths with mapnik PPA
Merge remote-tracking branch 'upstream/master'