Improve type error messages

[pelotom]

• Tweak the wording of the error message when giving an argument of the wrong type to a constructor... currently if you do something like

  var Point = Type({Point: [Number, Number]})
  Point.Point(0, 'foo')

  you'll get this oddly-worded error:

  wrong value foo passed to location second in Point

  With this change the message becomes

  bad value 'foo' passed as second argument to constructor Point

• Give a special error message for too many arguments to a constructor:

  Point.Point(0, 1, 2)

  will throw

  too many arguments to constructor Point (expected 2 but got 3)

[paldepind]

Yes. The current error messages are a bit weird. Throwing when too many arguments is given is a great idea.

I've left a single nitpicking comment.

[paldepind]

Thank you for this PR! Sorry for the delayed merge. I didn't realise that you had committed another change.