[MediaConsole] Added methods for creating servers

Two new methods have been added to the UPNP class, server_from_name and
server_from_udn.  These methods can be used to construct Device objects
from UDNs or friendly names, which is typically easier than using
the d-Bus path, which is long and changes from one invocation of
dLeyna-server to the next.

Signed-off-by: Mark Ryan <mark.d.ryan@intel.com>