Add a cental configuration structure

[ro-tex]

I think we should create an issue for this. It's def. a F/U but it's kind of an anti-pattern, we should init our API with a config object rather than overriding these vars from the outside. The config object is already a big improvement though.

Originally posted by @peterjan in #80 (comment)

[ro-tex]

Maybe add this named constant as well: #80 (comment)