Added new roads, adjusted detail layer, fixed tile palette flipx/y

[mwudunn97]

• Added new road assets and created prefabs
• Fixed Z-fighting with detail layer by adding random noise every time an object is placed
• Re-did map with new road assets
• Fixed tile flipping ('Shift' + '[' or ']') as previously this flipped all cells, but since we're using singular objects, it didn't flip the actual object
• Moved units 0.2 units up so that they are above the detail layer