plasma-sdk in kdereview

[Jonathan Riddell]

Plasma SDK contains a few handy developers tools for Plasma

plasmathemeexplorer, plasmoidviewer, plasmaengineexplorer and the icon
browser cuttlefish

It gets released with Plasma but is still in extragear.  I'd like to
move it to kde/workspace in git and I've just asked for it to be moved
into kdereview to start that.  Please have a review of it and see if
it's good enough.

Jonathan