Translations: Bugfix, drop columns, new defaults

[matentzn]

This PR:

• Changes a few default values for the new international edition
• Adds a new feature to drop unsupported columns during the preparation process
• Fixes a wrong references in the owl conversion of the translations

[gouttegd]

I approve, but please see my remarks about the use of a string-typed parameter in the config file (both for the newly added drop_unknown_columns and the other parameters added in #1006). They should really be boolean parameters.

(I am not requesting any change since it’s my fault for not having caught this mistyping before. Your call whether you want to change the type or not.)

[matentzn]

Thank you, I also tested your suggestion and it works perfect.

[gouttegd]

Glad that you agreed with the proposed change, but then it should be done correctly. It’s not enough to assign a default value of True or False – the option itself needs to be declared as bool. Otherwise you’re merely declaring a string-typed option that happens to have a default value of True or False.