Help: Create proper identifiers for keywords in QtHelp.

This is necessary in order for the QHelpEngineCore::linksForIdentifier API
to work.

 http://doc-snapshot.qt-project.org/qt5-5.3/qhelpenginecore.html#linksForIdentifier

That API is used by QtCreator to enable contextual links to help files.
Help: Add context to titles in QtHelp.

This allows disambiguation of identifiers in Qt Assistant and Creator.
Merge topic 'qthelp-context-fixes' into next

d107949d Help: Add context to titles in QtHelp.
b5002631 Help: Create proper identifiers for keywords in QtHelp.