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.

MyTracks/libs/README.txt

@@ -0,0 +1,17 @@
+The libraries contained here in binary format are licensed according to their
+own licenses, which allow their usage for the My Tracks application. Any other
+applications that wish to use these files should consult the appropriate
+licenses or the JAR's authors.
+
+References are provided to the libraries:
+
+accounts.jar (Android accounts library):
+http://code.google.com/p/libs-for-android/wiki/AccountsLibrary
+
+google-api-client-*.jar (GData client):
+http://code.google.com/p/google-api-java-client/
+
+google-common.jar,
+googleloginclient-helper.jar,
+libmymaps.jar (Google My Maps upload library):
+Licensed exclusively for use in My Tracks and derived Android applications.