Mockup Toolkit lost, please restore on share.kde.org and fix wiki link

[Friedrich W. H. Kossebau]

Hi,

https://techbase.kde.org/Projects/Usability/HIG/MockupToolkit has a link to 
the Mockup Toolkit, but that points into the void.

I was told this one is one of some files that had been lost for unknown 
reasons on share.kde.org.

So please reupload at least this one back and then update the link on the 
wikipage mentioned above.

Cheers
Friedrich