Avoid keyword errors

- fixes wrong camel casing when column names are all uppercase
- adds an additional underscore to the variable name for a column to avoid clashes with java keywords like `default` or the likes
- moves the mapping from column type to DataAffinity into the `DataAffinity` class
Yep, good point. :+1: 
We should stick to Locale.US here I'd say.

Once we have a customisation DSL in place, this should be adjustable by the user.