Change AstakosClient to use ASTAKOS_AUTH_URL as entry point to the
Astakos service, instead of ASTAKOS_BASE_URL it was using until now.

Remove ASTAKOS_BASE_URL from Cyclades settings, replace it with
ASTAKOS_AUTH_URL. Modify Cyclades to determine ASTAKOS_ACCOUNT_URL and
ASTAKOS_UI_URL with calls to astakosclient.