utility function: ncomp.
Merge branch 'dev' into world-state
paths getter function
added a macro to define path types.
Merge branch 'dev' into world-state
Merge branch 'world-state' into world-state-visualisation
Repl starts with repl and doc used.
spawn circle test function uses road/truck.
layer-from-world-state function: iterates over world state and returns a grid drawable constructed by a function argument.
example of path getter.