doc: Ensure page name does not change

This fix ensures that the page name is
set only once. Also included are a few
internal documentation changes that
bring qdoc's internal terminology up
to date.

Task-number: QTBUG-31578
Change-Id: Ib52a5a9024533d5a695cee0055bf2bc4d9bc2af9
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>