Add http_header_max and http_postbody_max configuration variables.

- http_header_max:
	Maximum size of HTTP headers (in non SPDY connections).

- http_postbody_max:
	Maximum size of an HTTP POST body (both in SPDY and HTTP mode).

Right now Kore will simply DC the client, ideally we want to send
a 413 (entity too large) to the client however.

See modules/examples/module.conf for more.
Be more verbose when configuration errors pop up.