Permission integration to ads pages/routes

Closes #15

See merge request !5

# Conflicts:
#   routes/ads.js

Only render a page section if the logged user is authorized to

Reinforce middleware, and add a function
which authorizes for a given user and required level.

Middleware that passes the session's user to all templates
with the name `_user`

Pictures support

Closes #11

See merge request !4

Ads en général en fait

Closes #1, #2, #4 et #5

See merge request !1

FOR DEVS I strongly advise you turn "fix on save" param for eslint on vscode

Closes #4

Get rid of check equality parameter which would kind of wreck the
principle of hierarchy.
And turn function in a more idiomatic implementation, using
Express's middleware chain system.

Permissions Closes #3

Closes #3

See merge request !3

Place callback as last parameter
And checkEquality is now required