User Icons workaround

So far, we have been retrieving user icons live from the Minotar website. while this works fine 99% of the time, it sometimes fail on the one or other user and this screws up things like the 2D map, the settler test and others.

So I have written now a system that tries to download all current lot owner icons once a day and reloads them from there. If the user does not exist on the local storage, it will still fall back on the Minotar one but still download it for later use. In any case, we rely less on network connections to other servers and this should be a good thing.