ClassCastException when dealing with alternate CommandSender implementations

When interacting with BanHammer via rcon and Minecraft's command blocks, using certain commands incorrectly (i.e. 'bh check' or 'bh history' with no parameters) causes ClassCastExceptions. When used with command blocks, this crashes the server.

Instead of checking specifically for ConsoleCommandSender, we should check if the sender was a player or not, as these commands without parameters only make sense for Players (offline or otherwise).