Refactor source layout

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

[no changelog]

src/main/kotlin/events/FeaturesInitializedEvent.kt

@@ -0,0 +1,8 @@
+
+package moe.nea.firmament.events
+
+import moe.nea.firmament.features.FirmamentFeature
+
+data class FeaturesInitializedEvent(val features: List<FirmamentFeature>) : FirmamentEvent() {
+    companion object : FirmamentEventBus<FeaturesInitializedEvent>()
+}