Calculate MD5 of (unencrypted) file and store in metadata.
Make it visible via file properties.


WHen we wish to use wuala to distribute for example ISO files of linux 
distributions, then we have the problem of "file integrity"

Almost all distributions have the MD5 checksum of the iso files published
somewhere on the webpages, so the integrity of the downloads can be verified.

For example for ubuntu you find them here:

http://mirror.switch.ch/ftp/mirror/ubuntu-cdimage/hardy/

It would be nice if wuala calculates the MD5 of the file (before encryption) and
stores it in the metadata.
In the userinterface in the properties of a file this MD5 checksum should then
be displayed.

That way a potential downloader of the file knows before downloading if the 
ISO file is "clean"

Example fo ISO collections:

http://www.wuala.com/Linux%2C+Ubuntu+%26+Co/ISO-Images