Use type aliases PluginPath, PluginPaths...

... for wxString and vector thereof, when holding plugin paths (which may or
may not be interpreted as file paths, depending on the module); to be replaced
later with different types

src/effects/Effect.cpp

@@ -158,7 +158,7 @@ EffectType Effect::GetType()
    return EffectTypeNone;
 }
 
-wxString Effect::GetPath()
+PluginPath Effect::GetPath()
 {
    if (mClient)
    {