Add support for floating bikeshare bikes

[barbeau]

Currently we show icons for bikeshare docks in OTP Android when the user enables the "Rental bike" option.

However, there are some bikeshare deployments that don't have physical docks - these are referred to as "floating bikes", and users identify their location via an app (bikes have GPS installed on them). In this case, the docks can be virtual hubs, or areas where the user is encouraged (or required) to return the bike. Currently, in OTP Android we're displaying floating bikes as racks with an availability of 1 and a capacity of 0. This should be changed to a new icon for floating bikes - we'd also need to handle the API response appropriately to distinguish between docks and floating bikes.

We currently support virtual bikeshare docks and free floating bikes in our OTP fork for our campus, the USF Maps App:
http://maps.usf.edu/#layers

Enable the "Share-A-Bull Bikes" layer to see the floating bikes and virtual docks/hubs (we don't have physical bike docks, but just geographic areas where they encourage riders to leave bikes). Trip planning via "Rental bike" will also give you a trip plan that picks up the closest floating bike (in real-time) and drops it at a virtual hub.

We're using OTP to consume a GBFS feed and expose bikeshare via the OTP API, both for the trip plan and the bike/dock locations. Here's the API endpoint for the bike/dock locations for our USF Maps App:
http://maps.usf.edu/otp/routers/default/bike_rental

...and official OTP docs for this API:
http://dev.opentripplanner.org/apidoc/0.15.0/resource_BikeRental.html

The USF Maps server is also currently the server for the Tampa region (we include HART and PSTA data as well), so we can test using Tampa.