Improved proxy support

• Refactor of existing proxy systems
• • Tunneling vs. forwarding is an explicit configuration choice, and no longer implicit based on tls properties. The behavior of existing applications should remain unchanged.
• • Implemented a new proxy "strategy" system for authentication. Strategies exist for no authentication, basic authentication, and synchronous strategies are now in place to support kerberos and ntlm authentication. Strategies can be linked together in a chain and attempted sequentially. Existing authentication controls remain in place but are deprecated and now map to the new strategy types.