Reviewing merge request #7: improve interface of Turtle.set_xy
Turtle.set_xy(pos, share, pendown)
Turtle.set_xy(x, y, share, pendown)
Some calls to Turtle.set_xy were already assuming the new interface. Plus, it makes it easier to write Primitive objects for blocks using Turtle.set_xy, since the x and y coordinates do not have to be packed together into a tuple.
Also fix a small bug in the 'bullet list' block of the 'presentations' palette. (The parentheses behind get_active_turtle were missing.)
Commits that would be merged:
change interface of Turtle.set_xy to set_xy(x, y, share, pendown)