Make preSN support production-ready

[JostMigenda]

Before any final release, we should

• finalise time bin size
• check whether the --mode argument is necessary or whether we can determine that automatically based on the model name
• make sure all models are working with the latest release of snewpy (I think that mainly affects Odrzywolek, now?)
• … and update the documentation

Originally posted by @JostMigenda in #61 (review)