Specify binlog_format in master and slave roles

The default is statement-based replication, which is unsafe in certain circumstances:

http://dev.mysql.com/doc/refman/5.5/en/replication-sbr-rbr.html

MIXED is MySQL's midpoint between statement- and row-based replication; it's as far as I know what you usually get by using Percona's config wizard. Whether the default is STATEMENT or MIXED, I believe this should at least be configurable.