allow 1 for boolean params - fixes #1840

sample xml from [DescribeDBParameters documentation](http://docs.aws.amazon.com/AmazonRDS/latest/APIReference/API_DescribeDBParameters.html) and [DescribeEngineDefaultParameters](http://docs.aws.amazon.com/AmazonRDS/latest/APIReference/API_DescribeEngineDefaultParameters.html) (with some modifications) and a second bool pulled at random from [mysql documentation](https://dev.mysql.com/doc/refman/5.0/en/server-options.html#option_mysqld_enable-pstack)