checkpoint skeletal matrix code.
Checkpoint non-working state.
checkpoint -- barebones cxn but fill does not work yet.
Bug fixes.
Checkpoint.  Can now construct with expressions like below.

  // Simple case: Entirety of shape specified, single element grain (implicit).
  var m = new ParallelMatrix([3,2,2],
                             function (i,j,k) { return i*100+j*10+k; })

  // Interesting case: Overall shape, with coarse (submatrix) grain explicit.
  var m = new ParallelMatrix([3,2,2], // overall shape
                               [2,2], // construction grain
            function (i) {
                return new ParallelMatrix([2,2], // subconstruction shape
                  function(j,k) { print("i:"+i+" j:"+j+" k:"+k);
                                  return i*100+j*10+k; });});

If you hand back a non-Array, non-ParallelMatrix when doing subconstruction,
you get an error:

  var m = new ParallelMatrix([3,2,2], // overall shape
                               [2,2], // construction grain
            function (i,j,k) {       // whoops...
                return i*100+j*10+k; // double whoops.
            })
  typein:11:4 Error: expected grain with shape:[2,2] but found subarray
Init skeleton for Debt token.