Better handling of Islands (La Réunion at least)

[kent1D]

In this screenshot, two things which could be better:

• We don't know what's the island in the center (La Réunion, France)
• The main city of this island is not "Le port" but "Saint Denis"

[kent1D]

Same problem here where:

• The island in the center is Mayotte
• The main city of this island is Mamoudzou

[kent1D]

The first problem should be addressed when we will use the exported boundary file ans the country.csv following this PR :

https://github.com/tilery/mae-boundaries/pull/7