Add opts argument to reply() in IRCMessage

All message sending extensions are supposed
to be implemented via opts from now on.
All message classes must have
reply(text, opts) method, with opts being a hash.
Add generic permission-checking API to Router
Implement DCC plugin
Add checks for 'can_use_dcc_chat' to DCC
Rewrite DCCBot using Gserver class
Implement SSL chat in DCC
Allow to configure chat and schat in DCC
Don't depend on message for permission API in Router
Rework DCC auth

Quickly deny connections that are determined to be from
the users that have no 'can_use_dcc_chat' permission.
Add .dcc_kill command to DCC
Add command dispatching helper to IRCPlugin
Use permissions and command dispatch in Loader
Add .raw and .kill commands to Manage
Use permissions and command dispatch in Manage
Add .raw_ctcp command to Manage
Fix left stripping in DCC
Add transmission context field to messages
Rely on message contexts in Menu and URL

This should put the end to abuse of replyTo field
in this role.
Add .demonstrate command to Manage
Add reusable help extraction method to Help