(refs #32)Separate Plugin interface and implementation

src/main/scala/plugin/Plugin.scala

@@ -0,0 +1,15 @@
+package plugin
+
+import plugin.PluginSystem.{Action, GlobalMenu, RepositoryMenu}
+
+trait Plugin {
+  val id: String
+  val author: String
+  val url: String
+  val description: String
+
+  def repositoryMenus   : List[RepositoryMenu]
+  def globalMenus       : List[GlobalMenu]
+  def repositoryActions : List[Action]
+  def globalActions     : List[Action]
+}