Support to access mybatis configuration properties from template

[kazuki43zoo]

Allow accessing to Configuration#variables from a template as follows:

Configuration

Configuration configuration = new Configuration(environment);
Properties variables = new Properties();
variables.setProperty("tableName", "persion.names");
configuration.setVariables(variables);

SQL Template

SELECT * FROM /*[(${tableName} ?: 'names')]*/ names
  WHERE ...

mybatis-thymeleaf translate to:

SELECT * FROM persion.names
  WHERE ...