[enh] Rely only on app_id argument for multi-instances apps
[enh] Rely only on app_id argument for multi-instances apps

The original app_id hard-coded replacement in scripts and hooks is replaced by
the use in app scripts directly of the given app_id argument (wip #126).
It's now the app maintainer responsability to make use of it in a way to
prevent colisions with other instances.

YunoHost/moulinette-yunohost,YunoHost/moulinette-yunohost,YunoHost/yunohost,YunoHost/yunohost,YunoHost/moulinette-yunohost,YunoHost/yunohost,YunoHost/yunohost,YunoHost/moulinette-yunohost,YunoHost/moulinette-yunohost