Incorporate Proxy into MCP-Gateway

[kpprasa]

We want to simplify and therefore incorporate proxy provisioning into the MCP gateway so that new containers can have a proxy to connect to.

This should eventually incorporate retries, location, and logging.

Sensible ratchets:

• Pass location header #69
• Pass just a static string for proxy to mcp-getgather #71
• Do verification of proxy and maintain blacklist #72
• Introduce custom configurability from client to gateway for proxy #73