Reduce the amount of up front work in performing introspection

Previously, when using PyUNO over a remote bridge, each remote
call which returned an object could result in 50+ further calls
to query interfaces on the result, regardless of whether and
how the object was then used. The majority of these queries
were made under css.script.Invocation to pre-cache certain
information about the returned object.

By making better use of available information to eliminate
interface queries which are certain to fail, and lazily
acquiring those interfaces which are required, remote scripting
is significantly accelerated. In general, this also gives a
small speedup for local scripting.

Change-Id: I4f36da6b5f09cb0d22f21291f05fbea2ae7ae697
Signed-off-by: Stephan Bergmann <sbergman@redhat.com>