Datacenters: add Frankfurt eu-central-1
Update map and countries.index after adding Frankfurt eu-central-1 region
Add ability to calculate all possible regions from close to far instead just one

We need to have a list of available regions for one of our projects, so instead
putting the nearest region only I added all regions sorted. Based on the available
region list we then can select one of the best option from it. To not break existing
file format, I added two more versions ends with `-alternatives`.