Expand Hafas vehicle and platform layout parsing

This now includes support for common.tcpdL and common.stc*L responses,
as well as support for multiple train groups in I.JF remark messages.

There's still more common.tc* fields and I.X* remarks that seem related
but where I have no idea about their content so far. At least neither of
them seems contain the per-coach load information that SBB seems to have
in this context.