Xfce4-about reworked

[Nick Schermer]

Folks,

I've create a branch that contains a new version of xfce4-about. I've
updated the whole thing to reflect the current state of the
contributors. The list of translators is generated from the Transifex
server (will be committed every week automagically). The branch
contains some new strings to translate (ie, the whole dialog is
translatable now, apart from language names), most if this was never
translatable, so not an issue IMHO.

The list of transaltors is here:
http://git.xfce.org/xfce/xfce-utils/tree/xfce4-about/translators.h?h=nick/xfce4-about

To the translators: MAKE SURE YOUR NAME IS CORRECT OR ELSE FIX IT IN
TRANSIFEX! Only translators in a translation team are added and if
your username != "mmassonnet" ;-).

The new lineup of developers and contributors:
http://git.xfce.org/xfce/xfce-utils/tree/xfce4-about/contributors.h?h=nick/xfce4-about

For core developers I only added folks who contributed significant
amounts of code for 4.8/last 2 years, so the list got a bit shorter
:/. Dropped the leading position of Olivier, kinda nonsense if you ask
me, but if people disagree: I only need to uncomment it.
Other people were added or moved around. I DID THIS QUICKLY SO PLEASE CHECK IT!

I intend to merge this after pre1, probably sunday, maybe sooner. Its
a big pile of code, I know, but it needed some love and not very
critical for desktop usage.

Nick