Document Coach Shuttle Gathering example

In the docs, in chapter 3, add the coach shuttle gathering:

• in the examples overview table
• And as a section (similar to the exciting sections), including:
  • a problem description subsection that includes a list of all hard and all soft constraints
  • problem size subsection. Run the CoachShuttleGatheringImporter class and it should spit that out in the console. Then clean it up manually by adding some spaces to align the numbers.
  • Hint: copy paste from the flight crew scheduling example docs, as that has the bare minimum and for coach shuttling the bare minimum docs is exactly enough.