[RendererConsole] Added methods for creating renderers

Two new methods have been added to the Manager class, renderer_from_name and
renderer_from_udn.  These methods can be used to construct Renderer 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-renderer to the next.

Signed-off-by: Mark Ryan <mark.d.ryan@intel.com>