Added switch to toggle off/on free tracks

Fix of crash when noise barrier is selected

* Fixed crash in certain parameters (with support from the Final Patch)
* All tracks are modifiable free edges after construction (with support from the Final Patch)
* Change of menu entry from Rail Depot to Asset/track_design_patterns
* Crash under campaign mode should have been fixed

Fine tune on tunnel entry

* Rework on terrain implementation to have zig-zag-less and smooth terrain cutting
* New thinner and realistic wall models
* Improved model collision detecting to help construction easier
* Bugfix on slope model error on switches, crossover and track ladders
* Added brick tunnel entry

Fixed crashes when choosing length x 1000 = 1

* Added "Road stacking over tracks" pattern
* Added some extra spacing in Crossover pattern to adapt some other station mods
* Fixed crash bug when noise barrier is choosen

* Fixed crashes on tunnel entry

* Reimplementation of models and model positioning algorithm to have non-overlapping, non-flickering walls or bricks

* CommonAPI support