udm_cat_list() returns array
listing all categories of the same level as current category
in the categories tree.
The function can be useful for developing categories
tree browser.
Returns array with the following format:
The array consists of pairs. Elements with even index
numbers contain category paths, odd elements contain
corresponding category names.
$array[0] will contain '020300'
$array[1] will contain 'Audi'
$array[2] will contain '020301'
$array[3] will contain 'BMW'
$array[4] will contain '020302'
$array[5] will contain 'Opel'
...
etc.
Following is an example of displaying links of the current level in format:
Audi
BMW
Opel
...