Review Request: shadowBlur and shadowText libplasma functions

[Jamboarder]

http://reviewboard.vidsolbach.de/r/64/

This patch exports a shadowBlur function and add a shadowText convenience function for libplasma.
Folderview will be patched so that the title uses the shadowText function.  Other areas of plasma might find this function useful as well (krunner and perhaps Plasma::Icon comes to mind).