rose edit: fix change meta or project flag.

This fixes changing the =meta or =project variable
within a rose edit session. Due to the old code's
reliance on `ConfigNode` data, which is not updated
as often any more, the update of the metadata does
not get triggered. This change adds the ability to
source the meta or project flag from the variable itself,
which is more correct.

@matthewrmshin, please review.