moved matrix class from utils to samples

samples/matrix/float32.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Emulates the browser's Float32Array (so Matrix4 can be used outside
  * the browser.
  * (Note this stores entries as 64-bit doubles, since there is no
  * 32-bit float type on the vm.)
  */
 class Float32Array {
   final List<double> buf;
 
   Float32Array(int size) : buf = new List<double>(size) {
     for (int i = 0; i < size; i++) {
       buf[i] = 0.0;
     }
   }
 
   double operator [](int i) {
     return buf[i];
   }
 
   void operator []=(int i, num value) {
     buf[i] = (value != null) ? value.toDouble() : 0.0;
   }
 }