* remove methods getConversationContexts() and
startNewConversationContext(). Note that these methods have NOT been
in any orchestra core release.
* add method createConversationContext(parent)
* add removeAndInvalidateConversationContext(context)
* don't time out contexts that have child contexts.
Have a ConversationContext keep track of its child contexts directly. In
particular, we need to know whether a context has children in order to
know whether to apply timeout checks or not; contexts with children
should never time out.
* Make API backwards compatible with Orchestra 1.1
* Name change for readability: "topmost" -> "root"
* Add @since1.2 to all new methods
* comment out a few methods that are never called from anywhere (yet)
* a couple of minor method renames
* Remove method ConversationManager.getOrCreateTopmostConversationContext, which is
equivalent to getOrCreateConversationContext().getRoot()