Register InteropServer as a well-known singleton

Issue #86 is caused by the server object being gc'd at the server. This
can be prevented by registering the server object as a
WellKnownServiceTypeEntry and specifying that the service be provided as
a singleton. This guarantees that the lifetime of the server object will
be the lifetime of the server process.
Merge pull request #90 from dcharbon/feature/prevent-disconnection

Register InteropServer as a well-known singleton