warcserver: SOCKS proxy:
- add support for running warcserver through a socks proxy specified via SOCKS_HOST and SOCKS_PORT
- move socks patch setup, http max_header adjustment to http module
- logging: print stack trace only if debugging
- add pysocks to extra_requirements, enable in ci
- add simple test (not actual proxy) to check that connection through proxy is attempted
- docs: add SOCKS proxy section to docs
