Choose what quotes to use in the insert feature to avoid the need to escape

Created by: migonzalvar

Instead of escape quotes in insert statement generation it tries to use double quotes when single quote are present in the value.

It adds 2 tests with strings containing ' and " and another one to check ASCII extended characters conversion.

Finally, I also changed in test_sql.py make_insert_statement(self) to test_make_insert_statement(self) and fix a method call from _prepare_rows_for_serialization() to to_rows(serialize_dates=True).

I know this is not a fully database specific solution (see #86 (closed)) but IMHO I think it's better than current situation. At least it works, for me :-).