Added Region Filtering for Capitals & Map Improvements

[Alog1]

Hi! I've been playing the game and wanted to add a few features to the capitals mode. I'm quite inexperienced, but I've tested every change extensively and everything seems to work perfectly.

Changes I made:

1. Updated elements.json to assign correct regions to all capitals
2. Added region filtering to capitals mode like in the countries mode
3. Added a "Show Country Borders" toggle in Settings, so that you can see country borders in the capitals mode
4. Moved the coordinates for Rome slightly (Rome was almost completely hidden by Vatican City) and I removed an undefined city at 0.0 (off the west coast of Africa), since I could not identify an island to which the city could belong.

Please let me know what you think of it!