put //gong:ident into doc comment, not free floating comments

[thomaspeugeot]

Situation:

//gong:ident parsing allows renaming to propagate to static identifiers

It is currently used in the gongdoc package to reference meta information

    //gong:ident [ref_models.Astruct]
    __GongStructShape__000000_NewDiagram_Astruct.Identifier = `ref_models.Astruct`

Problem:

This is a free floating comment, not a doc comment.

Resolution:

• [ ] when marshalling a stage,
  • [ ] create a map with the list of identfiiers in gong:ident
  • [ ] generate, for each identifier an exportable const string with the matching doc link comment
  • [ ] for each instance, have the fields with gong:ident initialized with the matching const string
• [ ] when unmarshalling a stage
  • [ ] parse the const string declarations and initiate the map
  • [ ] intercept assignments with a variable
• [ ] automate the whole

[thomaspeugeot]

Well, field renaming does not work