Resolve "refactor vars"

Closes #2 (closed) #9 (closed)

• I have changed TheRojam variables to E-lie variables because, as said, the latter were more flexible and consistent with Ansible good practises.
• I have tested the changes and the role still works perfectly.
• Readme in English / French with variables changes (suggestions for evolution are welcome!).

default/main.yml

@@ -10,7 +10,7 @@ ynh_extra_domains: ~
 ynh_ignore_dyndns_server: False
 
 # The list of Yunohost users.
-ynh_users: ~
+ynh_users: null
   # - name: user1
   #   pass: p@ssw0rd
   #   firstname: Jane
@@ -18,7 +18,7 @@ ynh_users: ~
   #   mail_domain: domain.tld
 
 # The list of Yunohost apps.
-ynh_apps: ~
+ynh_apps: null
   # - label: Tiny Tiny RSS # Label is important, it's a reference for the Playbook.
   #   link: ttrss # It can be the name of an official ynh app or a git repo link
   #   args: # Provide args here. Domain and path are mandatory, other args depend on the app (cf manifest.json of app).