make compatible with build 35716, which introduced an error (newly assert that no nodes are in the same location + add no matching fixes to the construction logic).

fix mesh era_c_sattion_sign_lod0

6 new stations from the game (era c) + little makeover

bugfix + some refactoring

Some fine points for edge cases

prettier pedestrian tubes

bugfix

add features to change bridge, track and tunnel types

optimise some lods and the stone bridges

neater pedestrian bridges + more options for walls