Also:
- Add get_conversation_messages() to PluginAPI
- Make plugins_autoload colon-separated instead of space-separated
(for consistency)
- Replace a JID() with a safeJID() in the uptime plugin
Plugins do not need to escape the command arguments or remove the line
breaks and care about how the will get parsed anymore, they just need to
pass a list of args.
Do not spawn an additional shell, for more clarity, simplicity and possibly
security.
