Fix order-dependent force handling: if a version is forced in one place, it is forced everywhere.  Two JarLibraries might compare equal even though their force setting is different; we want force to be dominant.

Reviewed at https://rbcommons.com/s/twitter/r/1085/
Adding a list of dirs to exclude from the '::' scan.  The CmdLineSpecParser
now passes along the workdir as the one dir to exclude.