Template random operator

*Title: Template random operator.

*Description:
New template operator for generating random numbers. Will return an integer,
or value from/to specified input parameters.

*Documentation:

Generating random value. Optional input parameters.

rand( [min_val, max_val] )

Returns:
Random integer value. If imput parameters are used, it'll be from min_val to max_val.

Parameters:
'min_val' - minimum integer value
'max_val' - maximum integer value

Example:
Fetch a random articles under '/news', node 102.

{def $news_count = fetch( content, list_count, hash( 'parent_node_id', 102,
                                                     'class_filter_type',  'include',
                                                     'class_filter_array', array( 'article' ) ) )
     $news_article = fetch( 'content','list',
                            hash( 'parent_node_id', 102,
                                  'class_filter_type', 'include',
                                  'class_filter_array', array( 'article' ),
                                  'limit', 1,
                                  'offset', rand(1, $news_count )|sub(1) ) )}