Split the initialization code to config and radarData

[sakirtemel]

Why

Current example and the code in readme both suggest mixing the init script with the data. In a real case scenario, this makes the radar less maintainable and extensible. Moving the data as radarData helps maintaining the content in radar and helps for future developments easier such as having different data sources for the radar data.

[bocytko]

With #132 the entries and date have been extracted to a configuration file loaded in docs/index.html. Any forks can follow a similar approach (some do already) and decide to extract more fields into a configuration. The API for the ring_visualization is unchanged.