add new slope steps to track builder

add curve radius code
	current code uses fixed array values, no easy access to code to manipulate
	
bridge pillar collision
	where does TPF calc bridge collisions?

fix cargo exception
	finding the right string on stack should be doable
	see GetIndex string. (only in last TPF Version?)
	
disable street changes for "Sch�nbauer"
	
	
check file case sensitive check
	maybe could be done via a std file open wrapper?
	
make it possible to change construction menu
	somehow invalid cache, maybe yearTo can give a hint
	add new lua function to replace a construction menu
		find the TPF Repo for Construction
		find the right entry, free the construction.
			Problem: CommonAPI Thread allocs crashes TPF free
	replace UI with CommonAPI UI Code?
			
add mod storage into a savegame

can river be removed safely from a map?

Look for Camera Hotkey, why is PageUp PageDown hardcoded