Refactored Plugin into an interface, make Javaplugin and relevant code to attempt to actually load plugins

By: Dinnerbone <dinnerbone@dinnerbone.com>

paper-api/src/org/bukkit/plugin/InvalidDescriptionException.java

@@ -5,30 +5,31 @@ package org.bukkit.plugin;
  * Thrown when attempting to load an invalid PluginDescriptionFile
  */
 public class InvalidDescriptionException extends Exception {
-    private final Exception innerException;
+    private final Throwable cause;
 
     /**
      * Constructs a new InvalidDescriptionException based on the given Exception
      *
-     * @param exception Exception that triggered this Exception
+     * @param throwable Exception that triggered this Exception
      */
-    public InvalidDescriptionException(Exception exception) {
-        innerException = exception;
+    public InvalidDescriptionException(Throwable throwable) {
+        cause = throwable;
     }
 
     /**
      * Constructs a new InvalidDescriptionException
      */
     public InvalidDescriptionException() {
-        innerException = null;
+        cause = null;
     }
 
     /**
-     * If applicable, returns the Exception that triggered this InvalidDescriptionException
+     * If applicable, returns the Exception that triggered this Exception
      *
      * @return Inner exception, or null if one does not exist
      */
-    public Exception getInnerException() {
-        return innerException;
+    @Override
+    public Throwable getCause() {
+        return cause;
     }
 }