Differentiate non-EU VAT rates

[GregOriol]

A few commits ago, you have added a few non-EU VAT rates.
However, these are not handled in the same way at accounting level (MOSS, VAT number, ...).
So, not sure it is a good idea to mix EU and non-EU rates without differentiation.

There could be for example a column indicating if it is a rate applying per the EU system or not.

Also, maybe add a reference link to the documentation about where the data for those new rates comes from and how to handle them.