rose-rug-brief-tour: remove system calls.

SYSTEM is not a Fortran intrinsic subroutine.
rose-rug-brief-tour: pre command sleeps.
Reinstate accidentally removed task section.
Merge pull request #771 from matthewrmshin/rug-brief-tour.sleep

rose-rug-brief-tour: remove system calls.
Merge branch 'master' of github.com:metomi/rose into metomi-gh-pages