Change auto-documentation to generate markdown

I've made some changes, now it uses the commandtable, instead of hardcoding what commands are contained. It then looks at which are 'category'-commands, and which are leafs, and displays information differently for the cases. 

The page https://github.com/Proxmark/proxmark3/wiki/commands is made directly from the output of this patch. Currently, it is not super friendly for console reading, so perhaps we should have -h and -m (markdown) which uses different formatting but the same logic.