mod_rest: Allow empty @to to mean to=account is in normal XMPP Noticed an XXX in snikket-web-portal wrt needing to explicitly set @to in order to talk to 'self' services in Prosody, where to=nil is the same as to=account

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.