Bug fix download e file_upload

[dsinibaldi77]

If database is oracle then crash:

1. download operation

@cache.action()
def download():
    return response.download(request, dbincomugest)

2. file upload operation:

# doc is varchar2 field
# doc_file is clob field but in define_table in model
...
Field('doc', 'upload', uploadfield='doc_file'),
Field('doc_file', 'blob'),
...
id = db.table_with_clob_field.insert(doc = db.table_with_clob_field.doc.store(item.file, item.filename),doc_file=item.file.read())