Issue #121

My site is hosted behind a load balancer (which handles SSL) like this :
Internet --HTTPS--> LoadBalancer --HTTP--> Apache

For now, Shaarli generate http URL for the Ajax calls while my page is
called with https; with the latest browsers (firefox) i get some "mixed
content" errors and the autocompletion does not work.

To know if the web site is called with a HTTPS URL, Shaarli should
check the X-Forwarded-Proto header.

I changed the https detection in the 'serverUrl' function (works for me
:) :

    $https = (!empty($_SERVER['HTTPS']) &&
(strtolower($_SERVER['HTTPS'])=='on')) ||
$_SERVER["SERVER_PORT"]=='443' ||
(!empty($_SERVER['HTTP_X_FORWARDED_PROTO']) &&
(strtolower($_SERVER['HTTP_X_FORWARDED_PROTO'])=='https')); // HTTPS
detection.