Task #8888: Added open() and close() to RPC class to hide implementation details of __enter__ and __exit__

Task #8888: Service is a frombus listener, so inherit from new class AbstractBusListener -> refactored out duplicate code

Task #8888: added abstract class AbstractBusListener to listen on a bus, and let the user implement one simple handle_message method

Task #8899: Allow broker options to be specified in FromBus/ToBus constructor (final final fix for tests without auto-reconnect, hopefully)

Task #8531: small bugfix for mangled reply addresses in RPC messaging and added extra checks for failure of sending replies.

Task #8571, #7508: Reverted commits r32893 and r32894. Instead, make sure that *every* test that uses the runtest framework is invoked as a login shell, by changing runctest.sh

Task #8571: Made the three shell scripts firing off the Python messaging tests a login shell to make sure that system-wide login scripts are being executed and environment variables are properly set.

Task #8769: Avoid login shell in t_* tests, and fix build by using lofar_add_package instead of add_directory

Task #8531: start and stop listening can now be used without -with- which defaults to start listening now. refactored some code and added support in RPC for multiple arguments.

Task #8531: Remove support for Binary message content and ensure Strings are always unicode when sent. Also make sure 'content' is first positional argument for EventMessage due to the way the message factory works. This breaks TreeStatusEvents.py which should use named arguments instead.