Fix unable to parse csv file in web2py break CSV parsing when dynamic upload is used

[jvanbraekel]

Hello,

The PR #654, actually break the CSV parsing, when it was working previously... Specifically, in case of dynamic upload in web2py : when the CSV file is uploaded trough the application before import into the database. TextIOWrapper is then already used to convert the binary stream into a string one the second usage in csv.reader raise an exception.

An example of usage in web2py controller typically looks like this : db.import_from_csv_file(TextIOWrapper(request.vars.file_selector.file,encoding='utf8'))

Removing TextIOWrapper from the call don't work, because pydal, 'object' and 'base' class are expecting string and not binary data. Consequently, all the parsing/format tests check for hard-coded string values ( for instance "TABLE' and not b"TABLE"), thus crash when binary data is used.