Revert Plugin to Interface, added PluginBase

Fixed Tests, moved TestPlugin out of messaging

By: Feildmaster <admin@feildmaster.com>

paper-api/src/main/java/org/bukkit/plugin/PluginBase.java

@@ -0,0 +1,31 @@
+package org.bukkit.plugin;
+
+/**
+ * Represents a base {@link Plugin}
+ * <p />
+ * Extend this class if your plugin is not a {@link org.bukkit.plugin.java.JavaPlugin}
+ */
+public abstract class PluginBase implements Plugin {
+    @Override
+    public final int hashCode() {
+        return getName().hashCode();
+    }
+
+    @Override
+    public final boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null) {
+            return false;
+        }
+        if (!(obj instanceof Plugin)) {
+            return false;
+        }
+        return getName().equals(((Plugin) obj).getName());
+    }
+
+    public final String getName() {
+        return getDescription().getName();
+    }
+}