[Bleeding] Add missing methods to Bukkit class, fix non-static methods, and add a junit test to ensure both these problems will be caught in future.

By: Celtic Minstrel <celtic.minstrel.ca@some.place>

paper-api/src/test/java/org/bukkit/BukkitMirrorTest.java

@@ -0,0 +1,19 @@
+package org.bukkit;
+
+import static org.junit.Assert.*;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+
+import org.junit.Test;
+
+public class BukkitMirrorTest {
+    @Test
+    public final void test() throws NoSuchMethodException {
+        Method[] serverMethods = Server.class.getDeclaredMethods();
+        for(Method method : serverMethods) {
+            Method mirrorMethod = Bukkit.class.getDeclaredMethod(method.getName(), method.getParameterTypes());
+            assertTrue("Bukkit." + method.getName() + " must be static!", Modifier.isStatic(mirrorMethod.getModifiers()));
+        }
+    }
+}