[sql gen] Properly create UNIQUE index on non string column. Closes #13728492
Unique was previously detected in a loop triggered only for String columns.
usr/lib/python2*/*-packages/cubicweb/dataimport/
usr/lib/python2*/*-packages/cubicweb/server/
usr/lib/python2*/*-packages/cubicweb/hooks/
usr/lib/python2*/*-packages/cubicweb/sobjects/
usr/lib/python2*/*-packages/cubicweb/schemas/
usr/share/cubicweb/migration/