Dynamic bike-rental: handle add/removal of graphs.

Lazy-initialization of BikeRentalUpdater graph to cover the case
where a graph is added/removed dynamically while the updater is
statically spring-created once.
Bike-rental: Add real-time data flag on station.

This is useful for the web-service exporting the station list, as you
can't determine otherwise if the station bikesAvailable/spacesAvailable
values are meaningful (for static station they are the capacity / 2).
Bike-rental: make capacity correct for odd values.

In case of static values coming from OSM data.
Cherry-pick periodic refresh for auto-discover.