Refactor source layout

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

[no changelog]

src/main/kotlin/events/FirmamentEvent.kt

@@ -0,0 +1,38 @@
+
+
+package moe.nea.firmament.events
+
+/**
+ * An event that can be fired by a [FirmamentEventBus].
+ *
+ * Typically, that event bus is implemented as a companion object
+ *
+ * ```
+ * class SomeEvent : FirmamentEvent() {
+ *     companion object : FirmamentEventBus<SomeEvent>()
+ * }
+ * ```
+ */
+abstract class FirmamentEvent {
+    /**
+     * A [FirmamentEvent] that can be [cancelled]
+     */
+    abstract class Cancellable : FirmamentEvent() {
+        /**
+         * Cancels this is event.
+         *
+         * @see cancelled
+         */
+        fun cancel() {
+            cancelled = true
+        }
+
+        /**
+         * Whether this event is cancelled.
+         *
+         * Cancelled events will bypass handlers unless otherwise specified and will prevent the action that this
+         * event was originally fired for.
+         */
+        var cancelled: Boolean = false
+    }
+}