Allow QSD.name to be blank

After schema simplification, QSD doesn't use the name field anymore, and most (all?) QSD objects have a blank value for it. This is fine, except that the admin panel complains whenever you try to save a QSD object with a blank name. Thus, make the field blank-able.
Merge pull request #789 from learning-unlimited/qsd-allow-blank-name

Allow QSD.name to be blank