Fix the semantics of PORTAL_FRONTEND_URL

As previously defined, it causes problems as to locally override, one
had also to override the PORTAL_FRONTEND_PORT1 value.

So change the semantic to be only about the base URL, and compose the
whole URL when it is used in the docker-compose file.

settings.default.sh

@@ -145,4 +145,4 @@
 : ${PORTAL_FRONTEND_VERSION:=":2.3.3"} # Stable Config
 : ${PORTAL_FRONTEND_PORT1:="80"}
 : ${PORTAL_FRONTEND_PORT2:="443"}
-: ${PORTAL_FRONTEND_URL:="http://172.16.22.176:${PORTAL_FRONTEND_PORT1}"}
+: ${PORTAL_FRONTEND_URL:="http://localhost"}