dev_5_0: Add omero config append/remove subcommands with default value handling for omero.web.* variables

[knabar]

This PR addresses https://trac.openmicroscopy.org.uk/ome/ticket/11201

Changes included are:

• addition of bin/omero config append and bin/omero config remove so that configuration using lists of strings can easily be manipulated, e.g.

  bin/omero config append omero.web.apps '"webfigure"'
  bin/omero config append omero.web.apps '"webtagging"'
  …
  bin/omero config remove omero.web.apps '"webfigure"'
  

• addition of corresponding unit tests under test_prefs.py

• loading the default value from omeroweb/settings.py when a value is appended to or removed from a previously unset omero.web.* property.

  $ omero config get omero.web.server_list
  $ omero config append omero.web.server_list '["test",123,"omtest"]'
  $ omero config get omero.web.server_list
  [["localhost", 4064, "omero"], ["test", 123, "omtest"]]
  

--rebased-from #2030

[manics]

👍

Extract from my modified install script:

OMERO="$OMERO_SERVER/bin/omero"
TABsearcher='["Searcher", "searcher/plugin_config/right_search_form.js.html", "right_search_form"]'
WEBsearcher='"omero_searcher"'

CONFIGweb=omero.web.apps
CONFIGtab=omero.web.ui.right_plugins

if [ $CONF -eq 5 ]; then
    echo "Configuring OMERO web-apps"

    "$OMERO" config remove "$CONFIGweb" "$WEBsearcher" || true
    "$OMERO" config append "$CONFIGweb" "$WEBsearcher" || {
        echo "ERROR: Failed to configure $CONFIGweb"
        exit 2
    }

    "$OMERO" config remove "$CONFIGtab" "$TABsearcher" || true
    "$OMERO" config append "$CONFIGtab" "$TABsearcher" || {
        echo "ERROR: Failed to configure $CONFIGtab"
        exit 2
    }
fi

[manics]

One very nit-picky comment: If there are duplicate values append adds to the end, remove takes from the beginning.

[knabar]

@manics Is there a situation where order is relevant? Should we just make remove take the first matching element from the end of the list instead of the beginning? Or do we even need to offer more control (e.g. prepend, remove-last)?

[manics]

@knabar No, it was just a comment (c.f. the one from an earlier PR about empty vs [] being symmetric), I'm happy with the current behacviour.

[joshmoore]

@will-moore / @dpwrussell : comments?

[will-moore]

Looks good!

[joshmoore]

Merging. Leave guidelines for reworking the CI jobs to you, @sbesson.