Zerg Creep Stomach Upgrade

[MatthewMarinets]

Added the Creep Stomach Upgrade, which:

• Allows zerg buildings to survive off creep
• Allows Spine Crawlers to burrow off-creep
• Allows Spore Crawlers to burrow off-creep

Misc tasks

• Get the triggers working in the GUI triggers
• Make a client-side PR to add the item and description for generation

[MatthewMarinets]

Made the modifications external to the editor to test out my scripts (still not fully automatic, but getting close). Opened in the editor to make sure it's showing up properly and there's no errors.