IDtpl: Template engine based on PHP template scripts

This class implements a template engine based on PHP template scripts.

It assigns template variables that are stored in an array class variable.

The class processes a template by including it as PHP code that can access the template variables by accessing the entries of an array named $d.

The class captures the output of the included template file and can return it as a string or displayed as the current script output.

New version allows template_in_template calls.