Minor improvement of the desktop file

[ghost]

It is the same as #553 but without i18n.

[neobrain]

Can you describe the changes you have done so that people who don't know the freedesktop spec by heart understand what you did, and why?

[ghost]

I do not know by heart. I have just mimic other desktop files of popular apps (like Firefox) after some tests.

[Tilka]

@rydroid Before this gets merged you should squash the commits (with git rebase -i) and thereby remove the French changes from the git history.

[ghost]

Will it be ok for merging if :

1. I reinsert a newline at end of file
2. the file is not executable
3. I "rebase" to delete the french translation from the history
   ?

[delroth]

Yeah, these three fixes SGTM.

[ghost]

Now this should be finally ok.