FC-39 FC-34 FC-42 FC-40 FC-41 FC-32 Added blue-green deployment support

Added system message handlers to manage application instance lifecycle, for application participating in blue-green deployment. Also added some preliminary changes for configuring number of worker threads independently for each message listener thread pool.

Signed-off-by: Steffan Westcott <steffan.westcott@clicktravel.com>
I can't see a Javadoc here... yet.