rose_prune: use shell to delete localhost files

This allows extglob (bash and ksh) to be used, e.g. for negative match.
Merge branch 'master' into rose_prune_shell
metomi/rose#858: document opt conf ordering
metomi/rose#529: allow clickable headers
Merge pull request #862 from benfitzpatrick/529.doc-slideshow-header-click

#529: clickable documentation headers
Merge pull request #860 from benfitzpatrick/858.rose-opt-conf-doc

#858: document opt conf ordering
Merge pull request #851 from matthewrmshin/rose_prune_shell

rose_prune: use shell to delete localhost files