add alpha value to color class
cleanup
add dynamic shadow to GfxComponent

this might be due to another improvement soon; perhaps a
GfxShadow-Class?!
add shadow generation to GfxImage
add shadow generation to GfxRectangle
add shadow generation to GfxText; perhaps a slight cleanup might be a
good idea, check the code!
remove debug output
add almost empty GfxShadow file (currently unused)