*Title: Template functions for fetching related objects.

*Description:

New functions for fetching related objects have been added to provide handy
and fast-working method of fetching related objects of any type (made by
attributes of "Related object" or "Related objects list" type or on object
level).

*Documentation:

Fetching of related objects:

fetch( 'content', 'related_objects',
        hash( 'object_id',            object_id,
            [ 'attribute_identifier', attribute_identifier, ]
            [ 'all_relations',        boolean,              ]
            [ 'group_by_attribute',   boolean,              ],
       	    [ 'sort_by',              sort_by               ] ) )

Returns:
An array of related objects, or 2-dimesnsional array if 'group_by_attribute' is
true().

Parameters:

'object_id' - ID of an object we fetch relations for.

'attribute_identifier' - You can use either string attribute identifier or a
numeric attribute ID. This parameter is not required and it's default vaule is
zero, which means it returns objects that are related on an object level, not by
attribute. This is similar to 'related_contentobject_array' functional attribute
of a content object.

'all_relations' - true() value means that ALL relations will be fetched no matter
of their type (content object level or specific attribute).  (false by default)

'group_by_attribute' - true() value have sense only with 'all_relations' set to
true and means that output will be not just an array of objects (as usually),
but the next structure:

$related_objects_grouped = array(         0 => array( $object1, $object2 ... ),
                                   /* objects related on content object level */

                                  attr_id_1 => array( $object1, $object2 ... ),
                                  attr_id_2 => array( $object1, $object2 ... ),
                                   ...
                                     /* objects related by attributes */
                                );
i.e. objects grouped by attribute ID (or '0' for content object level).

'sort_by' - sorts the result in different ways. This parameter must be provided
as an array of arrays that define sorting methods. The first element of each
array must be the desired sorting method. The second element of the array must
be the sorting direction, it can be either true() or false() - ascending or
descending.

It acts the same was as 'sort_by' parameter of 'list' fetch function,
that is described here:
http://ez.no/doc/ez_publish/technical_manual/3_6/reference/modules/content/fetch_functions/list
but currently supports only next sorting methods:
 class_identifier,
 class_name,
 modified,
 name,
 published,
 section.
Using of other sort methods will lead to a error.

Example:

{def $related_objects_grouped = fetch( 'content', 'related_objects',
	hash( 'object_id', $node.object.id,
	      'all_relations', true(),
	      'group_by_attribute', true(),
	      'sort_by', array( array( 'class_name', true() ),
				array( 'name', true() ) ) ) )}

Returns all relations grouped in arrays by attribute ID, and then sorted by
class name and by object's name in ascending order.

                                                                  
Fetching related objects count:

fetch( 'content', 'related_objects_count',
       hash( 'object_id',            object_id,
       [ 'attribute_identifier',     attribute_identifier,  ]
       [ 'all_relations',            boolean,               ] ) )


Fetching of reverse-related objects (having this object as related):

(All parameters are the same)

fetch( 'content', 'reverse_related_objects',
       hash( 'object_id',            object_id,
           [ 'attribute_identifier', attribute_identifier, ]
           [ 'all_relations',        boolean,              ]
           [ 'group_by_attribute',   boolean,              ]
           [ 'sort_by',              sort_by               ] ) )

fetch( 'content', 'reverse_related_objects_count',
       hash( 'object_id',            object_id,
           [ 'attribute_identifier', attribute_identifier,  ]
           [ 'all_relations',        boolean,               ] ) )