clean up of dbs2 urls

Since I stumbled upon it today, I took advantage to make a clean up of the dbs2 urls and replaced them by the dbs3 one. We probably still need to get rid of the DBS2 code, so there is one place where I didn't touch it.

For the future, we could also set this variable in a single place and then just import it every where it's needed, though I don't know the best way/place to do this.
@ticoann please review