sfGraphics lexp: +RectangleShape, CircleShape
sfGraphics lexp: +RectangleShape, CircleShape

Also export the Shape base class.
Also fix any color-properties which were returned as const reference by using
luabind's copy-policy.
Also add addDrawableDefs() and addTextureProp() to improve code reuse.

Oberon00/jd,Oberon00/jd