Carpool Details: drivers should see how many Seat info

[engerm]

Currently drivers do not see seat information on their Carpool Details page.

They should be able to see their original "Number of Passengers" and an 'Available Numbers of seat available'.

The "Number of Passengers" would reflect the value in they specified; when this is updated then it would reflect that on the Carpool Details page.

The 'Available Numbers of seat available' (or some other language like that) would keep a current and accurate tally of: the number from "Number of Passengers" - the number approved riders for that carpool