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 ;) )

They are torn down on program exit (retracting all live IUs)

* Exceptions when trying to modify retracted IUs.
* Removal of IU also retracts it.

Manually integrated the following changes from b8466a (master 2015-11-13)

- Blackboard classes by hvanwelbergen
- Blackboard test by hvanwelbergen
- Payload merge fix by hvanwelbergen
- rsb Buffer fix (by myself) copied but inactive (not needed atm?)

Please refer to the logs of the legacy-str branch for a full history
of the respective changes.

(by ignoring nonexistent keys)

(for remotely triggered local-IU handlers, in order to let the
RPC call of the remote side succeed as it should).

ipaaca-python: It's now possible to specify a single string category interest on InputBuffer instantiation.