[#142, #130][s]

Fixes #142 by finishing the TODOs (adding new fields). The data is also
handled by the transitional backend code.
Adds data to country overview page (@shevski, do you like the icons?)
(#130)
Fixes small bug with marking review as rejected if rejected
Fixes small bug of handling submissions without prior entry properly
(dataset and country weren't getting entered)
Uses only the short dataset names (cf. #109) for field values
Updated spreadsheet page to hold the spreadsheet according to
configured key value (cf. #144)