Ticket #1615

Add the ability to have article-type field that would list certain topics as a dropdown. Say, Iraqi governorate names or sources. These have to be topic dropdowns, not just dropdowns of regular lists, because AaI will want to use those for frontend browsing (e.g. browse articles by governorate)

Implementation: In the "article type" screen, the user selects "add field". The user selects "topic drop down list" as the type, and then selects a "root topic". All the immediate subtopics under this topic would be in the dropdown list which will be shown in the article edit screen. In the database, this type would simply be represented as an int. Change the ArticleTypeField class to support the new type. In the template language, the designer should be able to print the selected topic number and name for this field. Localization required. Documentation required.

Estimate: 2 days article type screen + 1 day article edit screens + 2 days documentation/localization + 1 day template language changes = 6 person-days