Rebalances the shotguns

With some Technology tweaks:

• Enable the shotgun from the start instead of requiring Military technology
• Moves combat shotgun from Military 4 to Military 3 technology
• Moves piercing shotgun shells from Military 3 to Military 2 technology

These changes moves all shotgun techs one level down, which means that at no point is the submachine gun the superior weapon until uranium bullets. Making the shotgun available before any research also allows for some combat options for playthroughs with tech multipliers.

With Utility tweaks:

• Adds a minor damage and shooting speed boost increase to Military 4
• Reduced the magazine capacity of shotgun shells from 10 to 6
• Adds piercing to piercing shotgun shells so they sometimes shoot through enemies

The magazine capacity of shotgun shells is honestly ridiculous, with 19X damage compared to firearm magazines and this reduces it to 11X.