anchor: love.physics.newPrismaticJoint
  Creates a PrismaticJoint between two bodies.
  
  A prismatic joint constrains two bodies to move relatively to each other on a specified axis. It does not allow for relative rotation. Its definition and operation are similar to a revolute joint, but with translation and force substituted for angle and torque.
  joint = love.physics.newPrismaticJoint( body1, body2, x, y, ax, ay, collideConnected )
  body1 Body The first body to connect with a prismatic joint.
  body2 Body The second body to connect with a prismatic joint.
  x number The x coordinate of the anchor point.
  y number The y coordinate of the anchor point.
  ax number The x coordinate of the axis vector.
  ay number The y coordinate of the axis vector.
  collideConnected (false) boolean Specifies whether the two bodies should collide with each other.
  joint PrismaticJoint The new prismatic joint.
  joint = love.physics.newPrismaticJoint( body1, body2, x1, y1, x2, y2, ax, ay, collideConnected )
  body1 Body The first body to connect with a prismatic joint.
  body2 Body The second body to connect with a prismatic joint.
  x1 number The x coordinate of the first anchor point.
  y1 number The y coordinate of the first anchor point.
  x2 number The x coordinate of the second anchor point.
  y2 number The y coordinate of the second anchor point.
  ax number The x coordinate of the axis unit vector.
  ay number The y coordinate of the axis unit vector.
  collideConnected (false) boolean Specifies whether the two bodies should collide with each other.
  joint PrismaticJoint The new prismatic joint.
  joint = love.physics.newPrismaticJoint( body1, body2, x1, y1, x2, y2, ax, ay, collideConnected, referenceAngle )
  body1 Body The first body to connect with a prismatic joint.
  body2 Body The second body to connect with a prismatic joint.
  x1 number The x coordinate of the first anchor point.
  y1 number The y coordinate of the first anchor point.
  x2 number The x coordinate of the second anchor point.
  y2 number The y coordinate of the second anchor point.
  ax number The x coordinate of the axis unit vector.
  ay number The y coordinate of the axis unit vector.
  collideConnected (false) boolean Specifies whether the two bodies should collide with each other.
  referenceAngle (0) number The reference angle between body1 and body2, in radians.
  joint PrismaticJoint The new prismatic joint.