Commit first version of serialization / deserialization mechanism.

It appears to work fine already for Paths and Groups.

src/basic/Matrix.js

@@ -42,6 +42,8 @@
  * matrix multiplication).
  */
 var Matrix = this.Matrix = Base.extend(/** @lends Matrix# */{
+	_type: 'matrix',
+
 	/**
 	 * Creates a 2D affine transform.
 	 *
@@ -74,6 +76,10 @@ var Matrix = this.Matrix = Base.extend(/** @lends Matrix# */{
 			throw new Error('Unsupported matrix parameters');
 	},
 
+	_serialize: function() {
+		return this.getValues();
+	},
+
 	/**
 	 * @return {Matrix} A copy of this transform.
 	 */