Get a taxonomy image for any URL within the site

ATTENTION: this is an API function. 
An admin can then make a call to this function from their theme or other PHP code
to display the appropriate image.

This function extends the taxonomy_image_display() function.

The image will be found by the first match of a taxonomy term equal to:
  a. taxonomy term of the node
  b. nodetype
  c. name of the nodetype
  d. aliasname of the URL
  e. by the internal URL: from the full URL till the left most URL part
    for instance: URL = xxx/yyy/zzz
    first search on 'xxx/yyy/zzz'
    second search on 'xxx/yyy'
    last search on 'xxx'
  f. the default image, if any defined
