Default Decimal Formatting Loses Data on Save

I ran into an issue with a clients file where simply open it and hit save and the field `24,000` is truncated to `24`.

Would setting the decimal format to `.` by default be more logical for most peoples use cases?

Example:

```
#original csv exported from excel
date,income
01/01/01,"24,000"

# after opening in TableTool and hitting save
date,income
"01/01/01","24"
```

Reproduce the issue by opening the shown CSV in TableTool and saving it, then trace the decimal-formatting and CSV save path involved. Done means the income value remains 24,000 after opening and saving, while the requested default decimal-format behavior is addressed.

Written by the indexing model from the issue text.