[Tracker] Commited changes for tracked.desktop localization

[Luca Ferretti <elle uca libero it>]

The file trackerd.desktop enable the launching of tracked at login.

In gnome-session 2.19/2.20 was added the ability to show localized names
and comments for login-launched services. So I committed some changes to
enable localization for trackerd.desktop

Now there are 3 small issues/doubts:
      * should we move tracked.desktop from "root" to "src/tracked" or
        should we add a "data" directory to put this kind of stuff?
      * could someone review and suggest better name and comment to show
        in gnome-session-properties dialog? [1]
      * could someone check if relevant files are dist-ed?


Thanks, Luca.

[1] Name=Tracker
    Comment=Tracker indexer and search tool daemon