Game image assets file naming

[sei-bstein]

Game cards and maps are currently named using the guid of the associated entity. The problem here is that some instances of GB are hosted behind caching providers that are challenging to invalidate, so even if the user uploads a new image or asset, it gets the same name and won't be served by the cache provider until it expires.

Need to append a random token to new uploads or generate a random name and then store it so we can bypass caching restrictions.

[sei-bstein]

Ask is to no longer delete unused assets - we'd rather be able to access them later if we need.