Unlocked thread race could lead to quick event sequences
causing inconsistent payloads! Fixed by serializing via extra
per-thread queue (... should have always been so; mea culpa)

The C++ parser is very minimal and ignores section markers (in our
case there isn't really any need for different sections anyway).
Python expects one section [ipaaca] - the format of the files
is otherwise standard ConfigParser / ini:

[ipaaca]

transport.mqtt.host=localhost
transport.mqtt.port=1883

backend=ros

You can override any of those using an environment variable
e.g. IPAACA_TRANSPORT_MQTT_HOST for transport.mqtt.host

Backends are automatically detected at module initialization.
There will be a warning if more than one is available and
you didn't specify the backend config key, e.g. using the env:
export IPAACA_BACKEND=ros
or
export IPAACA_BACKEND=mqtt

TODO: ROS host / port configuration etc (but rospy probably
honors their normal env vars internally; not tested)

Py and C++ confirmed to work on Raspberry Pi/ARM

TODO: config files for all versions

The RSB backend and dependency will be removed. This commit contains
the Python port, which was straightforward and seems to work well.

TODO: the other languages, and configuration (with legacy parsing)

logger_set_log_level(LogLevel.SILENT)  # or from string, for configs:
logger_set_log_level('WARN')

Calls with invalid values will silently preserve the previous setting.

Also renamed '__...' fields for default loggers to '_...'

It is now identical to the other language versions (again).
The new name is not as nice semantically speaking, but changing
the Python version is the path of least resistance.

Recent addition of IntegerConverter in rsb0.14 seems flaky (it
seems Python will always send 64bit, and no conversion can be made),
-> now using 64bit types for transport everywhere revision numbers
are exchanged as an RPC result, i.e. all RemoteIU modifications
and ResendRequests (Also disabled our own legacy IntConverters).

Note: the ipaaca.proto Protobuf definition has not been changed,
for compatibility reasons. Java version contains explicit (int)
casts when protobuf objects are built. (TODO Discuss proto->64bit)

Tests between all three languages work (Netboot, rsb0.14,
protobuf2.6.1, spread4.4), tested with WOz+Cere+Billie.

It will call the teardown stuff then os._exit(...). Later, when the
backends are fixed, we could simply alias it to sys.exit again.

Usage:
 - use ipaaca.exit() at the end of every python script
 - do not forget to catch errors as well as KeyboardInterrupt and
   SystemExit (or their default handlers will hang at exit time, too)
 - you can call ipaaca.exit with ant int argument (like sys.exit etc.)

Change was requested to accommodate people who package the
directory from outside the soa script (i.e. standard tools ;) )