Allow to set full url for endpoints

This changeset allows to set full url for endpoints. The default is
still to use the {public,admin,internal}_{protocol,host} and port
variables. The {public,admin,internal}_url parameters override the
_protocol, _host & port parameters.

There were previously one parameter for each {public,admin,internal}
endpoint url component (protocol, host), but not port.
Adding more parameters to allow different port would add too much
parameters and still missing the path part.

Fixes Bug#1227742

Change-Id: I834be8ab0f160b24348d218197711e8ecc392f5b