* Add fetching MC versions and Console from the extensions API
* Address reviews, expose custom MinecraftVersion interface
* Rename of McVersion -> MinecraftVersionImpl; proper nonnull annotation
* fluent consoleCommandSource(), change MinecraftVersion#name() to versionString()
* Javadocs adjustments
* Create impl package and move `MinecraftVersionImpl` there
* api version bump
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Co-authored-by: onebeastchris <github@onechris.mozmail.com>
rtm516