#176 Add a new field to pub records for corrected ISBNs

[Ahasuerus]

We need a new field in the Publication record for "corrected ISBNs". Sometimes a publishes uses an invalid ISBN or the ISBN is not clearly stated in the book, e.g. when SBNs are used instead. By adding a new field for corrected ISBNs, we will be able to enter the ISBN/SBN/Catalog ID as it appears in the book in one field and a corrected ISBN in the other. The latter can then be used to link to Amazon and other online stores.