Should `Description` extends `InternationalString`?

[desruisseaux]

ISO 19157 defines an DQM_Description object with only two properties:

• textDescription: a mandatory character sequence.
• extendedDescription: an optional BrowseGraphic.

Having Description as a type distinct from InternationalString is a minor complication for defining a unified parameter API (#74). It is also a complication for users by adding an indirection level in the majority of cases where they only want the text description. Description may be easier to use if the textDescription property is removed and replaced by inheritance. In other words, Description would be considered as a character sequence with an additional property, which is an optional illustration.