#1 warn users if autotemplate feature is not used

[Kai Dietrich]

The autotemplate features allows easy creation of fully functional presentations. Without it users are often confused why their presentation doesn't compile with pdflatex. Now because of backwards compatibility reasons, the autotemplate feature is disabled by default. We should warn users if they did not enable autotemplate support and tell them what to do so their code will compile with pdflatex.