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 'dev' into world-state
Path now contains maps for converting a vehicle type to a road type and vice versa.
path duration.
a non-existent background is denoted by nil or the absence of the
background key
Made add-building public