Add mobs to guard loots

[Arckenver]

Add ability to spawn mobs with loots so they protect them, and so make them harder to get.

[Arckenver]

We could add a node in lootConfig like this

mobs {
    Zombie=5
    Skeleton=3
    Spider=1
}

[Arckenver]

Fixed as of commit fb5ed5c.

[Arckenver]

To add loot guardians, add these nodes in config file

options {
    lootGuardians {
        Zombie=5
        Skeleton=3
    }
}

Specify mob type using official EntityTypes and the number of entities of this type to make spawn.