Remove the PITS code.

The code was not functioning properly and I don't even remember how it
worked anymore.

I will leave the spec file around in case a poor soul encounters it
and decides to build it properly.
Add some more flags to TransportConfig.

Specifically a flag to tell us whether we are in external/managed
mode, and a flag to tell us whether we are client or server. These
will be useful so that transports can configure themselves during
setup().
Don't pass TransportConfig to the transport __init__().

Passing it to setup() is enough. Transports that need it on __init__()
can keep it on their state.