reorganising logically the documentation

Hello,

i'm reorganizing the documentation to have everthing in folders and minimal files at the top

Cheers

created branch 3-reorganising-logically-the-documentation

closed via commit 7928f4ac

added Changed ~382 labels

changed milestone to %Manuals 1.0

added PJ2003-0343 label

changed milestone to %FusionDirectory 1.3.1