VstEffect: set displayName property at initialization

In VstEffect constructor set the displayName property in order to make
EffectView display actual plugin name rather than just "VST Effect".

plugins/vst_effect/vst_effect.cpp

@@ -69,6 +69,7 @@ vstEffect::vstEffect( model * _parent,
 	{
 		openPlugin( m_key.attributes["file"] );
 	}
+	setDisplayName( m_key.name );
 }