This allows the ability to override behavior of retrieving configured applications

Adds deprecation warning to starters

Document untrusted certificates when connecting to hystrix.stream endpoint

This moves the lifecycle of the eureka client of of EurekaServiceRegistry.

fixes gh-2099

Otherwise useServlet31 was always returning false.

fixes gh-2196

Signed-off-by: João Salavessa <joao.salavessa@sky.uk>