Update httpclient and httpcore to latest 5.1 release

Apache commons httpclient/httpcomponent 4.5 depend on commons-logging and not slf4j. This means that phoenix-thin requires explicit log4j configuration to work.

We want all logging to go through SLF4j, and to be able to use any supported backend.

Based on an an offline conversation with elserj

As these are new major version, it's probably going to involve more than a version bump.