First step of data flow refactoring.

This moves all data source connections into the TrackDataHub.

There are still many things to (re)do here:
- Optimizations about when the listeners are registered
- Optimizations about what data each TrackDataListener is interested in
- When activities are restarting, send new data since they were stopped (instead of doing a full reload)
- Proper double-buffering of Location objects (some listeners are interested in double-buffering all points, while others are only interested in double-buffering sampled points)
- etc.

MyTracksTest/src/com/google/android/apps/mytracks/io/CsvTrackWriterTest.java

@@ -0,0 +1,12 @@
+// Copyright 2010 Google Inc. All Rights Reserved.
+
+package com.google.android.apps.mytracks.io;
+
+/**
+ * Tests for the CSV track exporter.
+ *
+ * @author Rodrigo Damazio
+ */
+public class CsvTrackWriterTest extends TrackFormatWriterTest {
+
+}