Sampler and Optimizer files of OPAL-2.2.0 cannot be loaded

Sampler and optimizer files that are generated with OPAL-2.2.0 cannot be loaded due to the version number. Adding the line

self.__version_support = {
    '2.1.0': self.__parse_version_2_1_0,
    '2.2.0': self.__parse_version_2_1_0         # OPAL-2.2.0 support
}

would fix the problem. However, we should do a more general approach in order to avoid this error in future.