This patch is a follow up to D2575/rP23728, D2596/rP23737, D2786/rP23752.
Currently champion elephants inflict a lot more damage than hero elephants, which seems odd, because it's typically the other way around. For comparison damage per second of other melee soldiers:
```
b , c , h
cavalry axeman : 9.2 , 18.4 , 36.8
cavalry spearman : 5.5 , 11 , 22
cavalry swordsman : 8.7 , 17.3 , 34.7
```
This patch:
* keeps champion elephant damage as is (i.e. 113 damage per second);
* changes hero elephant damage, costs, and loot to twice the champion's;
* reduces champion elephant crush armour to 20 (same as other champions; hero elephants already have the same as other heroes (25) and elephant archers the same as citizens (15));
* removes 5% walk speed penalty, to give melee elephants the same movement speed as elephant archers;
* increases hero elephant vision to 100, the same as the champion's.
See also D2496 and D2852.