Slow down station board and train position injectors

[galderz]

Both sets of injectors should be improved to read the timestamps in each of the entries, and delay consumption until next timestamp.

e.g. station board

{"stop":{"station":{"id":"8500080","name":"Talhaus",..."timeStamp":1456761608798,..."@timestamp":"2016-02-29T16:00:11.418Z"}
...
{"stop":{"station":{"id":"8500081","name":"Altmarkt",..."timeStamp": 1456761611593,..."@timestamp":"2016-02-29T16:00:12.380Z"}

There's a difference of 2795ms between the two timestamps. We certainly don't want for users to wait precisely this time, but a a reduction of 4/5 times would provide a nice stable flow.

Similar timestamp information is available in the train position injector, so we should to coordinate them.