Move setup.sh and build_wheels.sh into main gwm repo.
Rework settings.

Settings are use the following precedence:
base.py is the defaults, then /opt/ganeti_webmgr/config.yml is read and it's
settings are used. Finally settings.py is used, if it exists.

Each settings file does not wipe settings from previous files, only
overriding settings it's defined itself.