Support multiple lines of the same option

  Some MySQL options need to be passed several times. For example :

  http://dev.mysql.com/doc/refman/5.5/en/replication-options-slave.html#option_mysqld_replicate-do-db

  This is currently impossible with the override_options. This patch allows to
  pass array as value. Example :

    override_options => {
      'client' => {
        'password' => 'xxx',
      },
      'mysqld' => {
        'bind_address'    => '0.0.0.0',
        'replicate-do-db' => ['base1', 'base2', 'base3'],
      },
    }

  Which will be evaluated into :

    [client]
    password = xxx

    [mysqld]
    bind_address = 0.0.0.0
    replicate-do-db = base1
    replicate-do-db = base2
    replicate-do-db = base3