Add setting for disposable time between transfers

[MichaelKutzner]

This adds an option to increase the time between transfers by a fixed duration. This setting can be used, if passengers want some time for orientation or to compensate small delays.

[felixguendling]

please rename disposable -> additional

the word disposable seems not like a good fit
https://www.thesaurus.com/browse/disposable

[MichaelKutzner]

Any suggestions for a better name? Thank you for the fast reply
I'm also not sure, if the duration for the footpath should include this duration. Or if it should be split, e.g. FOOTPATH (duration=X, additional_time=Y)

[felixguendling]

I guess the user expects that (footpath time + additional time) < (departure time - arrival time)

At least I would expect that.

[MichaelKutzner]

That was my intention, to make the footpath duration and additional time more obvious. But as I wrote, I'm not sure what format might be good to avoid possible confusion. I think, it might also depends on how the feature will be used.