Lego tracks treated incorrectly by Tracklist generator

[BGMP]

The Tracklist generator is not handling Lego tracks correctly. When it picks a lego track one day, it puts the track in R mode for the following day. This is normal behaviour for regular tracks, but lego tracks don't have an R version.

We should probably add an attribute to the Track model to classify it as lego track, and then handle them differently at the generator. A few constraints that come to mind:

• Only 1 lego track per tracklist
• Pregenerate a pool of all lego tracks before beginning generation. For example, if there are 4 lego tracks, we would want 1 and 2 for the first 2 tracklists, and then 3 and 4 for the next two, not 1 and 2 and then 1 and 2 again.