initial redesigning widgets
fix widget delete bug
implement assignment operator and copy constructor for all widgets existing
widget2d setcolor implementation
rearrange widget constructors
minor naming
experimental widget casting functionality
explicit casting among widgets, removed implicit casting
PolyLine widget implementation
grid widget implementation
text3D widget implementation
clean unnecessary methods, make text3d face camera
Merge pull request #15 from ozantonkal/implementing_widgets

Implementing widgets