Expand namelist documentation

• Small tweak to kt_grids_single namelist documentation

• Small tweaks to kt_grids_range namelist documentation

• Add documentation for kt_grids_specified namelists

• Add documentation for kt_grids_box documentation

• Add documentation for kt_grids_knobs

• Add documentation for layouts_knobs

This PR also provides an improvement to the generated documentation. It now uses html tables as opposed to markdown ones. Whilst this makes the generated files a bit more complicated it is now possible to directly use markdown lists, ford regions (like @note) and more whereas previously these didn’t work and we had to use work arounds like using raw html in the in-source documentation. The added complexity should be fine as these source files are automatically generated from the code and are only used essentially internally to the ford processing.