Add methods to expose country-to-zone mapping and other meta data

[kashifshamaz21]

The official IANA timezone data src has information about which zones are used in a country and vice versa. It also has information about zone aliases(called as "links"). These are useful pieces of information for better handling of timezones.
For example: A user can be shown a list of countries to select from, and based on the chosen countries, a second list of zones used in that country can be pre-populated. To achieve such a functionality, a mapping between Countries-->Zones is needed.
This requires parsing of following files from the IANA tz data:

1. iso3166.tab: This file can be parsed to create the country-code to country map.
2. zone.tab: This file can be parsed to create the map between countries to timezone ids.

This type of functionality was added to moment-timezone library, so that can be used as a reference point if need be. (https://github.com/moment/moment-timezone/blob/develop/tasks/data-meta.js)
(https://github.com/moment/moment-timezone/blob/develop/data/meta/latest.json)
@jodastephen Thoughts?

[jodastephen]

Some of this was covered in the Joda-Time-I18N project. Its not been updated in years, but could be a useful base. Adding this to the core of Joda-Time seems like overkill.

[irfn]

@jodastephen Using a single source of timezone data is important in an application and for a java application, joda seems appropriate. Any links such as location info should change whenever core timezone info changes. From this perspective i see the need for a single library to be the source for this.
i18n is a one of effort to get the translations and locale specific intricacies nailed down and i doubt the library owner/community would appreciate needing a release whenever a location decides to change their timezone. If you dont deem this change fit for joda itself, we may need a new small library.