Improve ImageFileValidator to make use of PHP 5.2's image_type_to_extension()
Rename $formats to $aliases, added "tif" aliases
add CHANGELOG entry
Merge 8774a3d...a88dfe1 (from pr-1480)

closes #1480

* pr-1480:
  a88dfe1 add CHANGELOG entry
  8b5bbb8 Rename $formats to $aliases, added "tif" aliases
  8774a3d Improve ImageFileValidator to make use of PHP 5.2's image_type_to_extension()