Compatibility with Smarty 5

[s-hamann]

It seems that as of version 5, Smarty uses a namespace, which is incompatible with how Self Service Password currently uses Smarty.
Trying to access Self Service Password with Smarty 5.3.1 (probably any 5.x version) results in an HTTP status code 500 and the following error logged:

PHP Fatal error:  Uncaught Error: Class "Smarty" not found in /var/www/ssp/htdocs/index.php:213

I fixed this locally by either adding use \Smarty\Smarty; to index.php or instantiating $smarty as new \Smarty\Smarty();. I can't tell if this breaks compatibility with Smarty versions 3 and 4, though.

[coudot]

Smarty 5 seems very young for the moment, we focus our efforts to Smarty 4 by now.

[s-hamann]

In that case, I suggest updating the Prerequisite section in the README.md to reflect that users should not currently try running with Smarty >= 5.