Fixes #42

When scanning a file / set tracks are iterated and handled differently based on the is_foldable field. In the case where it foldable it is locally defined as group and in the case where it isn't it is defined as track. Later in the function it is assumed that track is already defined. However this won't be the case if the track was foldable / was a group. As a result the follow error is raised:

                for device_index, device_data in enumerate(track_data["devices"]):
>                   device = Device(track, device_index, device_data["name"])
E                   UnboundLocalError: local variable 'track' referenced before assignment

To reproduce: add a device to a Group and then try to instantiate a Set with scan=True

Changes

• Rename the local group instance to track (it is technically a track and this resolves the unbound issue since it will then be defined later in the function)
• Adds an EQ Device to the first Group track in the Tests.als file. (see note below about Live version of the Tests.als file)

Testing

With the updated Tests.als file (and without this fix) the current tests will break when the Set fixture attempts to init with scan=True. With this fix, the issue is resolved.

NOTE: I'm on Live 12.0.1 and as such am only able to save the Tests.als as a v12 Live file. If we're not comfortable bumping, someone may need to apply my change and save in the current v11 edition.