Minor tweaks to local setup

[olivas]

The commits are simple enough that they should be self-explanatory. A combination of a few one-liners, most of which are in documentation, but one to the bootstraph script as well.

[robsavoye]

Postgres uses the environment variables PGHOST, PGUSER, PGPASSWORD, so we should probably use those.

[emi420]

It also uses the configuration file in /etc/underpass/default.yaml

# Underpass config file
config:
    - underpass_db_url:
        - underpass:underpass@localhost:5432/underpass
    - planet_servers:
        - planet.maps.mail.ru
    - destdir_base:
        - /usr/local/lib/underpass/data/

[emi420]

But the change is good because those are local variables in the bash script.

Thank you @olivas for your contribution!