The CASC file to load: path when given (a relative one against
root), else config/config.casc under root.
A relative path is taken against the project root, not the working
directory, for the same reason the root is searched for: the program's
working directory is an accident of how it was started.
The CASC file to load:
pathwhen given (a relative one againstroot), elseconfig/config.cascunderroot.A relative
pathis taken against the project root, not the working directory, for the same reason the root is searched for: the program's working directory is an accident of how it was started.