Reduce assets size

[Nomagno]

See kimden#21

[kimden]

I am ready to contribute to it. Please assign me.

[Nomagno]

While the design is pretty hardcoded, track_overlay_database.xml allows to add collectibles to any track without having to package it, which accounts for 90-95% of the needs of TME. Many tracks could be simply removed from the packaging now.

[Nomagno]

I consider this fixed for my purposes. While it is not quite general, the track overlay database can be expanded with new functionality as needed, this could easily trim the assets back to normal size if desired for a future release (for now it's staying like this, as the default TME track variety is nice).

[kimden]

Uhh...