qdoc: Added module attribute to most index elements

qdoc: Added module attribute to most index elements

The index file generated by qdoc when it is run in
-prepare mode has been modified so that most elements
have a module attribute. The value of the module
attribute either came from an \inmodule command, or
it is the value of the project variable specified in
the qdocconf file that was read by qdoc.

Task number: QTBUG-27626

Change-Id: I44198bbbc1738fafc110c6b905eb1d67bc745323
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>