Add option to delete or archive old game sessions

[lordscales91]

Hi there, so the thing is that with the current implementation it seems like all the game sessions per each game are stored within a single JSON file, at least from what I can see. All those files are loaded when entering the game activity view. As it grows over time it will get slower and more resource hungry.

What I would like is the ability to delete or archive old game sessions. When it comes to archival, I suggest storing several JSON files per game in a different location, each file would contain all the game sessions for a particular time period, for example by year or month. Ideally the time period grouping should be a user configurable setting and the plugin should take care of splitting or merging those game sessions when the setting changes (with proper warnings to the user that it may take a long time).