mod_rest: Add configuration of which stanzas to route to callback Makes it simpler to build APIs that only handle a certain kind of stanzas, letting them be handled by the unhandled stanza handler instead of having to write code to ignore certain kinds of stanzas.

This module produces more detailed HTTP logs for Prosodys built-in HTTP
server. The format is similar to that of Apache and go into Prosodys
normal logs at the `info` level.