After this commit,
- chinese custom date are supported
- Possibility to specify the custom datetime format and not only dateformat.
Withtout it, impossible to import a date column and datetime column at
sametime with custom format.
- Add test to check import date with custom format
- Fix translation where error messages was in the source.
This commit fixes#13783 and closes#13803
Courtesy of @odony for the review ;)