Add new functions to configure spice port and ticketing. Yes, this is
incomplete, it includes just the most important bits to get something
up'n'running.
These functions are supposed to replace both spice_parse_args() and
the monitor interaction via qterm interface.
The implementation can't handle multiple spice server instances at the
same time right now. The API allows this though, so if we fixup the
implementation some day we don't have to change the API.
