Make subnavigation for variants configurable

[jensgro]

In older versions of Mandelbrot the variants appeared beneth the link of the module. In recent versions a second navigation opens.

Please make this design decision configurable.
If a user wants to stick with the old version, newer versions of fractal cannot be installed because the design decisions seems to reflect into the core-code of fractal.

For the time being users of the older mandelbrot version have to stick to at last fractal 1.5.2.