Introducing a vehicle page

[pietercolpaert]

A feature request to enable this kind of URL:

https://irail.be/vehicle/{route_id}?date={date}&from={stop_id}&to={other_stop_id}

This should give a nice overview of a vehicle's trip on that date, optionally highlighting the from and to station. When e.g., tweeted, facebooked, or slacked, this page can give a nice peek on delays, statistics on cancellations, how busy the train is, etc. in the metadata tags.

On this page, I want to see:

When route_id is set

• The name of the route (e.g., "Oostende → Eupen")
• The short name of the route (e.g., P8008)
• When no other parameters has been set, include a form allowing to fill out a date
• Future: statistics on how many times it has been delayed in the past?

When also the date is set

• The stops it is visiting with dots and lines (like a metro status map). The dots are further apart when the time in between is longer.
• The names of the stations with a link to their page on iRail
• The train occupancy (estimated, real-time or historic)

When also from stop_id is set

• Highlight the stop_id and add it to e.g., the twitter card summary

When also to stop_id is set

• Highlight also the end stop_id and the trip in between from and to

Other minor TODO:

• Change the link when clicking on a specific departure in the departure overview of a station

Should help fixing #100 #184 and #205