Added setPosition and setPositionRotation

teleportToPlayer and setPosition has some strange side effects. From
the player’s perspective they seem to have no effect. From another
player’s perspective, one can see the player teleport to the specified
location but immediately return to the original position. setLocation
uses Entity’s a(double,double, double) function. It successfully
teleport’s the player. Inspection of
a(double,double,double,float,float) and
b(double,double,double,float,float) appear to be the yaw and pitch
complements of 'a'. They however exhibit the same effects as
teleportToPlayer and setLocation. If fields x and y are set before
calling a(double,double,double), the player is successfully teleported
to destination with yaw and pitch set.