Replication configuration

This adds key configuration settings needed to set up replication.

Compared to the existing two pull requests adding server_id (and log_bin in one case), this one
- allows configuration of server_id, log_bin, binlog_format, max_binlog_size and expire_logs_days
- provides a default value for log_bin (at least for Debian based distros)
- also adds comments for the new parameters
- uses instance variable references ('@') in the templates