The identifier for groups/topics such as "Document" that have a class
with the samen name are suffixed with "Group", so the identifier becomes
"DocumentGroup". For groups/topics with no ambiguity the identifier
matches the topic name closely, for example "ExpressionFramework" for
topic "Expression Framework".
The documentation has topics, for example topic App which contains
namespace App or topic Document that contains class Document. This
commit makes sure that the topic has a link to the relevant class or
namespace, whereas the relevant class or namespace refers back to the
topic for a more high-level overview.
- The location of the documentation is improved (not in the cpp file
anymore but in core-app.dox). This prevents cluttering source with
high-level overviews typical of topic documentation.
- The formatting has been made consistent.
