LP#1552861: add upgrade script

LP#1552861: add upgrade script

Also, a test plan for the fix:

[1] Set the vandelay.default_match_set setting for several
    org units. In at least one case, set it to the ID
    of a valid vandelay.match_set entry; in another case,
    set it to a numeric ID that doesn't match any existing
    vms rows; and finally, in another case set it to the
    name of a match set.
[2] Apply the patch and run the database update. Verify that
    the update script will indicate that there are invalid
    settings, then delete.
[3] Open the library settings editor and verify that in the
    case where a valid match set was used, the editor provides
    a drop-down with possible vms values with the correct
    one selected.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>