Get licenses from plugins.

Fixes issue 2642.
Returns an InputStream because thats what the license panel uses for everything else.

Change-Id: I487257961ac40bb421ef8b8c92da32a221ce2ce9
Reviewed-on: http://gerrit.dmdirc.com/106
Reviewed-by: Gregory Holmes <greboid@dmdirc.com>
Tested-by: Gregory Holmes <greboid@dmdirc.com>

src/com/dmdirc/plugins/PluginInfo.java

 import com.dmdirc.updater.Version;
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
 import java.util.List;
      * This will load a ConfigFile
      *
      * @return the ConfigFile object for this plugin, or null if the plugin has no config
+     * @throws IOException if there is an error with the ResourceManager.
      */
     private ConfigFile getConfigFile() throws IOException {
         ConfigFile file = null;
         return file;
     }
 
+    /**
+     * Get the license for this plugin if it exists.
+     *
+     * @return An InputStream for the license of this plugin, or null if no
+     *         license found.
+     * @throws IOException if there is an error with the ResourceManager.
+     */
+    public InputStream getLicenseStream() throws IOException {
+        final ResourceManager res = getResourceManager();
+        if (res.resourceExists("META-INF/license.txt")) {
+            return res.getResourceInputStream("META-INF/license.txt");
+        }
+
+        return null;
+    }
+
     /**
      * Get the defaults, formatters and icons for this plugin.
      */