feature 1519: admin instructions are dispatched into several tabs. Only
applied to en_UK and fr_FR. The help content itself needs some updates
but it will be another set of commits, in this commit, I nearly only
modified the container.
The new "Add Photos" help page only introduces you to 3 main ways to add
photos: direct upload, pLoader and FTP. Each of them has a dedicated tab
on the Admin>Photos>Add screen.
No use of the big question mark icon linked to the Help pages in the
administration header, to avoid having this icon twice : in the header
+ in the content next to H2.