MDL-11741 - Convert core modules to take advantage of recent improvements to build_na...

MDL-11741 - Convert core modules to take advantage of recent improvements to build_navigation.

This check-in removes about 400 lines of code. I hope I have not screwed anything up. I would be grateful if people could review this change, and keep an eye on the navigation bar in modules.

Any navigation bar bugs you find in the near future, feel free to file them in the tracker and assign them to me. Thanks.

If not to many problems are found, I think I would like to backport this to 1.9 stable, but I am not sure that is a good idea. Opinions to the General Developer Forum please. I am about to start a thread there.