Enhancement for `ContentType` documentation

[romaintailhurat]

Several pieces are amiss in the ContentType documentation in 4.0:

• the intro doc needs to be reworked (e.g. it still refer to the xml:lang attribute)
• there is no inline documentation for the xml:lang substitute that is the MultilingualStringValue element

Also, for this last element, the type documentation - langString - could be completed with references to what is a langString and some syntax examples.

If this material is not already in the making, i can try to provide something (with a proper PR).

[DanSmith]

Hi Romain,

Yes, the MultilingualStringValue does need a description added, feel free to offer a PR.

The langString type is defined as a pair of a character string and a language tag.

Each serialization handles the langString type in it's own native manner. In XML this is done with the xml:lang attribute, in RDF the content is a RDF literal with type http://www.w3.org/1999/02/22-rdf-syntax-ns#langString and a language tag. In json it is a string and language tag pair.

Documentation for the built in COGS primitive type langString is found in https://github.com/Colectica/cogs-web/blob/master/docs/_sources/modeler-guide/primitive-types.rst.txt , If you'd like to expand the documentation there feel free to offer a PR for that as well.

[wlthomas]

New property needs documentation.