[kde-guidelines] Grunt work

[Aurélien Gâteau]

Did some grunt work today :)

* Added "Implementation" section to all control pages

* Refreshed Date_Time_Pickers [1]: new content, new screenshot. It needs more 
guidelines though, see [2]. 

* Refreshed KNS: new content, new screenshot.

* Refreshed Labels.

[1]: http://techbase.kde.org/Projects/Usability/HIG/Date_Time_Pickers
[2]: 
http://techbase.kde.org/Projects/Usability/HIG/Contributing#Projects.2FUsability.2FHIG.2FDate_Time_Pickers

Aurélien