Add libenv to manage composition of environment variables.  Add (ls)catenv to view the various env scripts in the library.  Add lsenv and lssrc to list environment and source dependencies without their own do files.  Reorient *.env files to be scripts instead of content.  Rename dodep to libdo, for coherent naming with libenv.  Clean up use of the string env in code: change most env to smith or var.