timeout ConnectionNotFoundException

[IldarKhayrutdinov]

When the timeout_ms expires the route method return ConnectionNotFoundException.
Tested on latest revision of master 796d42b

response content:
"{"message":"Connection between locations not found","hints":[{"message":"Connection between locations not found","details":"com.graphhopper.util.exceptions.ConnectionNotFoundException"}]}"

log message:
[dw-768 - POST /route] INFO c.g.http.MultiExceptionMapper - bad request: [com.graphhopper.util.exceptions.ConnectionNotFoundException: Connection between locations not found]

It would be nice to get a timeout exception.