* Scenarios contain a string map of feature flags. The flag names are the keys, and flag versions are the values, so a typical value might be "fixed" for bug fixes or for evolving features, "V1", "V2", etc.
* The game has a map of flags to lists of supported versions. The game can therefore signal that it supports a legacy behavior for a given feature flag. The last version in the list is considered to be this build version's default behavior.
* When launching a scenario, we check to make sure the game supports the scenario's required versions of its feature flags.
* When launching a replay, we make sure the game supports the feature flags that the version of the game that made the recording did.
Fix#555Close#591