Fixes SF2/VST title rename bug #462

Restores auto-name functionality to newly added SoundFont and VST tracks where the track name will take the name of the soundfont or vst plugin, respectively.

Tested with `.mmpz`, `.xpf` to maintain compatibility with tracks that have a name specified.

![screen shot 2014-05-26 at 12 55 19 pm](https://cloud.githubusercontent.com/assets/6345473/3084649/d30bc238-e4fc-11e3-9338-0ff0042ba6b2.png)