* Minz allow parallel sessions
#fix https://github.com/FreshRSS/FreshRSS/issues/3093
* Array optimisation
* Array optimisation missing
* Reduce direct access to $_SESSION except in install process
* Fix session start headers warning
* Use cookie only the first time the session is started:
`PHP Warning: session_start(): Cannot start session when headers
already sent in /var/www/FreshRSS/lib/Minz/Session.php on line 39`
* New concept of volatile session for API calls
Optimisation: do not use cookies or local storage at all for API calls
without a Web session
Fix warning:
```
PHP Warning: session_destroy(): Trying to destroy uninitialized session
in Unknown on line 0
```
* Only call Minz_Session::init once in our index
It was called twice (once indirectly via FreshRSS->init())
* Whitespace
* Mutex for notifications
Implement mutex for notifications
https://github.com/FreshRSS/FreshRSS/pull/3208#discussion_r499509809
* Typo
* Install script is not ready for using Minz_Session
* Remplace les tirets de soustraction par points médians ou des tirets
cadratins (si c'est trop long, nous pourrions mettre des
demi-cadratins).
* Met les abréviations des jours anglais en exposant, comme
`3<sup>rd</sup>`
