docs reorganization   added tutorial, racket categories   relabeled some other categories   normalized manual names: de-bolded, changed some names
docs reorganization
  added tutorial, racket categories
  relabeled some other categories
  normalized manual names: de-bolded, changed some names

original commit: 1b702a2ae32aba835f7467ced6b203902db0ccd9

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket