Small balance changes

Small bugs fixed.

Towers:

• +1 damage every other level instead of every level.

• Burn damage raised from *0.05 (5%) to *0.1 (10%) of base damage per skill point.

• Attack damage raised per attack stat point is +2/+3/+7 after having 0/7/15 stat points assigned.

Sun Flower tree: Burn damage raised from *0.05 (5%) to *0.1 (10%) of base damage per skill point.