Create DiscoveryAsyncHttpClient
Implement binding of discovery http clients
Be stricter about relative URIs
Move discovery announcer into its own package
Extract the code for dealing with the service pool.
Inject the HttpServicePool
Refactor tests to mock the HttpServicePool
Rename HttpServicePool with HttpServiceBalancer
Refactor ServiceDescriptorsUpdater out of CachingServiceSelector
Use ServiceDescriptorsUpdater to populate HttpServiceBalancerImpl
Remove support for loading service inventory over http/https.
Create a discovery HttpServiceBalancer from ServiceInventory
Use DiscoveryAsyncHttpClient for talking to discovery service
Rename DiscoveryHttpClient to BalancingHttpClient
Pass HttpServiceBalancer exceptions to ResponseHandler
Make ServiceUnavailableException not depend on type/pool.