Rebalance shields

The plan is to have all shields for nomads be stealth shields by default, so this needs rejiggling to make the existing ones work:
1. instead of 4 shields there will be three that upgrade into each other - T1.5, T2.5, T3 - The t3 stealth shield should be removed/hidden from the game.
2. All shields should use the default shield shader instead of the stealth shield shader
3. All shields need to upgrade into each other
4. The T2 shields will reuse the existing upgrade animation, and the t3 shield will not have one, until the models are redone.
5. some basic balance numbers need to be put in until apof fixes them.