smpp2sim: make the SCP81 BIP relay work

The BIP relay ( the "handset" side for SCP81) never worked: the
connect callback in handle_OpenChannel was "never called" as the fixme
says, everything else was missing.

Fixme cause: card APDU I/O is driven synchronously, proactive command loop
lives in a blocking while loop (pySim.transport.LinkBase.send_apdu_checksw)
that runs on the Twisted reactor thread. A Twisted TCP4ClientEndpoint +
connectProtocol only completes when the reactor does reactor things,
but the reactor thread is stuck in that loop for the whole proactive
session...

Fixme fix: don't fight the reactor, just drive the relay channel with a plain
old blocking socket, which fits the synchronous execution model.
Channel numbers now come from the command Device identities (channel_N ->
low nibble) instead of the hard coded chan_nr == 1.

Additionally fix two bugs found on the path to scp81 glory:
- TERMINAL RESPONSE device identities are forced to terminal->UICC per
  TS 102 223 6.8.2 (prepare_response() inverts the command identities,
  which for a channel-addressed BIP command yields channel_N->UICC).
- Error responses now build a valid AddlInfoBip cause, prepare_response()
  hard coded empty "additional information" cannot be encoded for a
  BIP error.

And some tests based on real card interactions.

Change-Id: If96c768f2e35c20ea3753e601059410121517b60
---
M pySim-smpp2sim.py
M pySim/bip.py
M tests/unittests/test_bip_relay.py
3 files changed, 539 insertions(+), 41 deletions(-)