Fix HTTP client now that Mojang has their stuff together.
Block really wrong offline mode names, see #1270
Don't send no permission message on tab completion.

Instead returns the empty completions.
Manually remove the player from everyone's tab list on disconnect

This is needed because when the player disconnects from bungee they are removed from the connection map, this causes the tab-list rewrite to fail due the player no longer being on bungee and therefor it ends up not removing the player (online vs offline uuid). This would only happen on servers without ip-forwarding enabled
Improve legacy client ping support.
Remove security manager