FIXED:
Now abusing a game mechanic, in order to prevent a bug from causing the track editor to crash on certain tracks

Some important changes in this one, so I will make it very clear:

Changes to the existing racetrack start+pits checkpoints:
1. I unlisted them in the track editor (unlisting instead of deleting means that existing tracks continue to function)
2. I updated the checkpoint hitboxes for them, so that the CPs can now be passed on both sides. From my testing, this results in a checkpoint that can always be passed. If you however DO run into any issues with existing tracks, please let me know ASAP.

Replacement racetrack start (w/o pits) checkpoint:
1. As a replacement, I added a new racetrack start checkpoint without pits, dubbed 'universal'
2. You can have the pits on either side, regardless of its rotation
3. This is a proper 1x1 tile, so do NOT place VOID/BIOV tiles next to this one
4. A downside of this approach is that the CP can be passed not only from the pits-side, but also the opposite side. This shouldn't normally pose any serious issues, but the checkpoint could be passed on the grass, or possibly from another part of the racetrack immediately adjacent to the checkpoint.

NEW:
- 3x3 arena turn
- field outside for 3x3 arena turn (choose 1 of the 3 outside tiles, replace the other 2 with void)
- arenafloor outside for 3x3 arena turn
- concrete outside for 3x3 arena turn
- arenafloor inside for 3x3 arena turn (choose 1 of the 3 inside tiles, replace the other 2 with void)
- concrete inside for 3x3 arena turn

FIXED:
- Size of two new WIP tunnel tiles was wrong (1x1 instead of 2x2)

NEW:
- flat arena straight tile
- flat to diagonal arena straight tile 1
- flat to diagonal arena straight tile 2

UPDATED:
- Added tile preview images for the extended industrial fencing (2x, 3x, 4x) and elevated racetrack crossing.

FIXED:
- in some conditions you could fall through the last few meters of Racetrack Bridge 3x extended
- issues with multiple 2x/3x extended walled raceway tiles (partial lack of collisions and/or visual issues)

UPDATED:
- Dynamics no longer spawn on top of the gantry of the racetrack start+pits checkpoint
- P1-8 and P9-16 starting grids now match with the racetrack start+pits checkpoint again after its overhaul

Updated racetrack checkpoint previews to align with their new model road textures.

Hotfix (folder with capital letter caused game crash on startup)

'Fixed' Racetrack checkpoints. Unfortunately the broken second row will probably not be fixed, unless the developers start patching the game again and undo what broke the checkpoints.

Improved model and textures of racetrack checkpoints, added placeholder new tunnel tiles. Feel free to use them already, though the models will change a bit in the future.