Retry Leaderboard Uploads

[Greenfoot5]

Currently, the game doesn't retry uploading the player's score if it fails. Which means that score also won't get another attempt (though technically two now that it tries to save after and just before a wave).

It also doesn't store the score in a failed attempt to try again later (either when the player goes to the leaderboard section or just the main menu).

Lastly, it still tries to connect even if the player doesn't have any internet. This isn't really neccessary and would ideally be cleaned up alongside this task.

This also relates to #83 but that more focuses on improvements to the server, this is code for the game only.