streetcar backend on backbone.js

main idea was to get rid of the ridiculous number of http calls, some
done twice, since the same data had to be shown in different places

now we have one backend that periodically fetches data for multiple
stops, any number of views can subscribe to that

since the data is kept up-to-date by the backend, and we have a
predicted timestamp "when the streetcar will arrive", we can now update
the view at a 1-sec interval to update the relative times
bugfix nav: clicking on the icon didn't work
page nav with history