#482 Provide better default messages and merge MessagesManager

- Return message from the JAR's messages_en.yml file instead of an unusable error for the end user
- Merge MessagesManager into Messages

src/test/java/fr/xephi/authme/TestHelper.java

@@ -0,0 +1,28 @@
+package fr.xephi.authme;
+
+import java.io.File;
+import java.net.URL;
+
+/**
+ * AuthMe test utilities.
+ */
+public final class TestHelper {
+
+    private TestHelper() {
+    }
+
+    /**
+     * Return a {@link File} to an existing file from the main (non-test) resources folder.
+     *
+     * @param path The absolute path to the file
+     * @return The project file
+     */
+    public static File getJarFile(String path) {
+        URL url = TestHelper.class.getResource(path);
+        if (url == null) {
+            throw new IllegalStateException("File '" + path + "' could not be loaded");
+        }
+        return new File(url.getFile());
+    }
+
+}