Improve Output of Search algorithms

Nobody has claimed this yet.

The current implementation of our search algorithms simply output a list of stops without considering lines / transfers.

To allow reasonable annotation, we should augment the output of the transit search algorithms.
This output should probably consist of the following information:

- a list of stops and the line used to reach it - here we might need to distinguish between actual lines (from the data) and what is internally used as line. This could require a dedicated ID ?
- all transfers and their ID to allow correct annotation (type/...)

Possible further annotation requirements will be added to the ticket, as they arise.

Start by tracing the transit search algorithms and the current output that lists stops. Determine how routes, lines, transfers, and transfer IDs are represented in the existing GTFS-based data and search results. Done should mean search results expose enough stop, line, and transfer information for correct annotation, but the issue leaves the exact design and further requirements open.

Written by the indexing model from the issue text.