refactor the Head class to remove _sphere and use default copy constructor
remove unused GLUQuadric sphere from Avatar class
use the default Avatar destructor, comment out unused consts in Head
change the iris texture
fix the width and height for the new iris texture
repair indentation in Head constructor
remove a lingering comment
Merge pull request #338 from birarda/avatar-refactor

refactor the Head class to not keep its sphere and use default copy constructor