Robotics Service Bus

Support hierarchies of participants in rsb/**/*.py

fixes #1828

A parent participant can now be specified when a new participant is
created. The request-reply module specifies:

• {Local,Remote}Server instance as parents of {Local,Remote}Method
  instances
• {Local,Remote}Method instances as parents of their Listener and
  Informer instances

• rsb/__init__.py (createParticipant): accept parent keyword parameter;
  pass to participantCreationHook
  (createListener): accept parent keyword parameter; pass to
  createParticipant; extended documentation string
  (createInformer): likewise
  (createLocalServer): likewise
  (createRemoteServer): likewise
  (createServer): similar
• rsb/patterns/__init__.py (LocalMethod.makeListener): pass self as
  parent to createListener
  (LocalMethod.makeInformer): similar
  (LocalServer.addMethod): similar
  (RemoteMethod.makeListener): similar
  (RemoteMethod.makeInformer): similar
  (RemoteServer.__getattr__): similar
• rsb/introspection/__init__.py (ParticipantInfo.__init__): added
  parentId attribute
  (ParticipantInfo.getParentId): new method; accessor for parentId
  attribute
  (ParticipantInfo.parentId): new property; parentId
  (IntrospectionSender.addParticipant): accept optional parent
  parameter; if supplied, store parent id in ParticipantInfo
  (handleParticipantCreation): accept optional parent parameter; pass to
  IntrospectionSender.addParticipant
• test/coretest.py (HookTest.setUp): record parent participant for
  following check
  (HookTest.testInformer): check parent participant
  (HookTest.testListener): likewise
  (HookTest.testLocalServer): likewise
  (HookTest.testRemoteServer): likewise
• test/introspectiontest.py
  (ParticipantInfoTest.testConstructionWithoutParentId): renamed
  testConstruction{ -> WithoutParentId}
  (ParticipantInfoTest.testConstructionWithParentId): new method; test
  constructing ParticipantInfo objects with parentId