Adding private branch plugins

Private are:
* not ready for publishing (not enough comments/need refactoring/etc)
* not suitable for publishing (uses private custom services)
Adding ejabberd_resources plugin
Adding ejabberd_connections plugin
Adding more ejabberd plugins
Adding new ejabberd_scanlog error types

EJAB-1583 patch event logging
Add ejabberd_resources_ plugin and it's image
Replace ejabberd_{s2s,users} with ejabberd_stats_