* test printableextractor with various aspell/pspell versions

Untested code:
* the ASF extractor may or may not work -- I could not find an ASF file with
  meta-data so far :-(.
* dito for QuickTime: it may or may not work


Promising extractors that probably deserve to be written:

image:
* tiff

text:
* dvi (creation date, page count)
* man pages (title, modification date, authors, brief description)
* info pages

office:
* rtf 
* Microsoft doc
* StarOffice sdw
* Microsoft ppt
* Microsoft xls

video:
* mpeg
* avi

code:
* Java (@author, @version, classname, inner classes, brief class description)

packages:
* deb 
