This class enables you to handle a template whose input is not a file but directly a string.
To be always as efficient as possible, it uses cache if it evaluates that it could be faster.
But when string templates are cached, they are saved on the filesystem and use some disk space. It's the reason
why there is an option enabling to forbid it to cache a template if you think that it's not required to have
a big efficiency. It will be the case for instance when you know that a string template will be used only once a month.