Caching proxy enhancements

Add ICAP (RFC 3507) client capability to version 3 of Squid web caching proxy. Content previews and all MUST-level client-side features of RFC 3507 must be supported, including handling of ISTags.

Squid 2.x (written in C) has several ICAP client modules/patches, none of which is good enough for migration to Squid 3.x (written in C++) though some low-level code can be reused. The final code must be stable, production-quality code. Initial design and testing assistance will be provided.

Squid is a popular open source proxy cache, licensed under GPL. This project would require understanding of Squid internals, which is not a trivial task on its own.

Project duration is 60-70 calendar days.