- plugins: simplify integratePlugins(); ...

* CPluginsExec(): switch to singleton
* move CPluginsExec() to pluginlist.cpp|h
  because it's not really a settings_helper

src/gui/pluginlist.h

@@ -67,4 +67,11 @@ class CPluginChooser : public CPluginList
 		int run ();
 };
 
+class CPluginsExec : public CMenuTarget
+{
+	public:
+		static CPluginsExec* getInstance();
+		int exec(CMenuTarget* parent, const std::string & actionKey);
+};
+
 #endif