Improvements to map selection menu

1) Remove the tilde sign (~) from all area references. "Flat area: ~1.5 km2" -> "Flat area: 1.5 km2" For an irregularly shaped entity such as an island, it is implicit that surface areas provided will not be exact, but approximate. The tilde sign adds little or nothing, but removing it improves clarity.

2) Add ability to sort or filter the islands. Currently only 4 islands, but this problem will get bigger as more islands are added. Sort by total area, flat area, alphabetical, difficulty, unplayed islands, etc.

3) Add a mouse hover over function for the various icons (currently 8) to the right of the island map. There is for example a cryptical icon followed by "1,300k". For a beginner player it's not exactly obvious what all these icons mean. Mouse hover over would display in plain text what the icon means, like "Iron ore".