add data on elections at federal and county level

[Sebaristoteles]

This data will probably at the Wahlkreis-level and needs, therefore, a correspondence table to the counties.
This might involve adding a new level of "Wahlkreis" for all calculations. Just at this level and the state level, information on elections can be displayed.

[Sebaristoteles]

Integration done.
See #36 for development of stories.