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".
(cherry picked from commit dce6ae9a7d)

plugins/vst_effect/vst_effect.cpp

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