Adding new filetypes

To add icons for .docx documents, please do the following:
copy core\images\icons\16\doc.gif -> core\images\icons\16\docx.gif
copy core\images\icons\32\doc.gif -> core\images\icons\32\docx.gif

edit the following files (make a backup copy just in case):
- core/js/ckfinder_ie.js
- core/js/ckfinder_gecko.js
search for
"doc|"
and replace it with
"doc|docx|"

Empty browsers cache.