Bike-rental: Add JCDecaux Open-Data API, various tweaks.

List of modifications (each is a commit, by chronological order):
- Addition of the new JCDecaux Open-Data API (see https://developer.jcdecaux.com/), tested with real-time from Nantes (Bicloo network).
- Handle dynamic multi-graph with static bike rental updaters: cover the case where an updater target graph is dynamically created or removed via the web-service API.
- Add "realTimeData" flag to the bike rental station list web-service to help users distinguish between static and dynamic data.
- Correct computation of total capacity for static OSM data for odd cases (make sure that bikes+free=capacity).