started SDFLoader

The SDFLoader reads a text file and composes a scene object which can
be rendered later. The Shape class is just dummy code, so that the
loader can recognize the define directive within the text file.
added "make"-functions

Memberfunctions of Scene implemented
Shape und Sphere extended

Various changes have been made… ;-)
Added Virtual Friend Function Idiom

Now using operator<< to print shapes to the console.

See http://www.parashift.com/c++-faq/virtual-friend-fns.html for more
details.
Minor changes
Minor changes
Merge branch 'pansit'