Allow the retrieval of the plural rule type for a given number

Allow the retrieval of the plural rule type for a given number

For example, find out which rule type should be applied for 5 items
in Arabic. The result would be 'few'.

This implementation should be non-disruptive and completely backwards
compatible (which is the main reason it isn't a lot simpler).

Change-Id: I3d72e4105f6244b0695116940e62a2ddef66eb66