This is in preparation for HAFAS wagonorder support

this avoid race conditions when a user changes their checkin between the time
of request (old trip id) and the time of data update (new trip id). These
could lead to funny effects such as buses suddenly having S-Bahn carriage
formations.

Decreases severity of #99
Fixes #108

Closes #126

Note that this is more of a hotfix -- the underlying bug is in
Travel::Status::DE::HAFAS

(cherry picked from commit 5d8f6467dc00f03957784230983ed730ec421291)
Signed-off-by: Birte Kristina Friesel <derf@finalrewind.org>

locationSearch uses mgate.exe, just like the regular departure board.
similar_stops_p relies on ajax-getstop.exe which may become unavailable sooner
rather than later.

Still TODO: handle stations that have several EVAs