**Motivation**
Ribbon makes heavy use of Archaius in a static manner for configuration.  This pattern couple Ribbon with legacy archaius and its dependencies and makes it hard to run tests in parallel. By decoupling from both archaius and statics users can now provide alternative configuration mechanisms as well as improve testability.

**Changes**
- Introduce a new DynamicPropertyRepository abstraction to decouple from Archaius specific APIs
- For legacy support make the ArchaiusDynamicPropertyRepository discoverable via the service loader.
- Allow a non-static DynamicPropertyRepository to be associated with a IClientConfig.  This is a bit of a hack but minimizes code changes.
- Decouple all build.gradle dependencies from archaius, except for the ribbon-archaius subproject
- Pick up @zone from DynamicPropertyRepository and NOT from archaius's DeploymentContext
- Remove configuration for PollingServerListUpdater as it is not used and would always require static configuration

Also:
* As had to change the mocking of DiscoveryClient and InstanceInfo in some tests, refactored out that mock code into 2 static methods on LoadBalancerTestUtils.
* Upgraded eureka-client dependency version from 1.4.6 to 1.7.2 to get the EurekaClient.getEurekaClientConfig() interface.

Added getReachableServers() and getAllServers() API
and deprecated the less clean getServerList(boolean) API.

Changed IClientConfig interface. Move ClientConfigBuilder to be an inner class of IClientConfig. Added example of load balancing using URLConnection.