Allows for code like
CacheConfig config("MXS-2727");
config.storage = std::string("inmemory_storage");
config.soft_ttl = std::chrono::seconds(1);
config.hard_ttl = std::chrono::seconds(10);
config.max_size = 10;
config.thread_model = CACHE_THREAD_MODEL_MT;
config.enabled = true;
to be used when you want to create a configuration manually and not
from a configuration file.