Leave out the quadrant part.

Let it grow!
Remove trace and rename pickBrick to nextBrick.
Attempt to fix faulty location picking.

Previous code would give blocking locations only for the brick
passed to model', where the entire list is expected.

This in turn apparently gives double entries.
Add helper function modelNextBrick.
Add two new ways of generating a model.

mmodel generates a brick model with exactly 10 bricks, given StdGen.

mmodel' generates a brick model, adding 10 bricks, appending to m.
Uses StdGen  as random generator.
Print out all models as lists of location tuples.
Formatting of the model output.