Refactor source layout

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

[no changelog]

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

@@ -0,0 +1,8 @@
+
+package moe.nea.firmament.features.texturepack
+
+interface BakedOverrideData {
+    fun getFirmamentOverrides(): Array<FirmamentModelPredicate>?
+    fun setFirmamentOverrides(overrides: Array<FirmamentModelPredicate>?)
+
+}