This is to allow for reading in "options" blocks that may apply to
module-sets later, even if the needed module-set hasn't been read-in yet
(e.g. if it's contained in a common file meant to be included in some
but not all configurations).

To do this right we need to decouple the actions of reading options and
then later applying them to the various OptionsBase subclasses. This is
a start toward that.