Refactor source layout

Introduce compat source sets and move all kotlin sources to the main directory

[no changelog]

src/main/kotlin/features/texturepack/NotPredicate.kt

@@ -0,0 +1,18 @@
+
+package moe.nea.firmament.features.texturepack
+
+import com.google.gson.JsonElement
+import com.google.gson.JsonObject
+import net.minecraft.item.ItemStack
+
+class NotPredicate(val children: Array<FirmamentModelPredicate>) : FirmamentModelPredicate {
+    override fun test(stack: ItemStack): Boolean {
+        return children.none { it.test(stack) }
+    }
+
+    object Parser : FirmamentModelPredicateParser {
+        override fun parse(jsonElement: JsonElement): FirmamentModelPredicate {
+            return NotPredicate(CustomModelOverrideParser.parsePredicates(jsonElement as JsonObject).toTypedArray())
+        }
+    }
+}