write.py: After the bsddb version has been upgraded, if the schema versions also needs to be upgraded, output a separate dialog asking the user whether he wants to upgrade the schema. (As requested by Benny).

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21887 4ae1f11a-8b86-4847-b8af-ab372f36d1fd