[gameplay] Tweak Ranged spreads, reduce archer spread, tweak cosmetic stats.

The major change here is that Archer spread is reduced to 2 to make them have much better aim than before at max-range, where they often missed. This makes their DPS more predictable over their range.

This makes ranged unit's spread proportional between citizen soldiers, advanced/elite CS, champions and heroes.

Because of the spread reduction and because promotion more strongly reduces spread, the 10% spread reduction from the archery tradition technology is removed.

Gravity values are tweaked.
LaunchPoint values are raised and standardised by unit type.

Patch By: Nescio

Differential Revision: https://code.wildfiregames.com/D3374