Multiple improvements to the data hub:

* Making registration finer-grained so we only listen to the data we really need.
* Moving the system listener registration to an external class (for testability and readability)
* Adding a unit test (not yet complete)
* Adding documention and cleaning up comments

Still many things TODO:
* Allow pausing of registrations
* Add pause/resume to onPause/onResume of activities
* Move sampling logic out of the hub
* Optimize data reloading when display preferences change
* (maybe) move the data hub and related classes to the "content" package

SignalStrengthSamplerTest/default.properties

@@ -0,0 +1,11 @@
+# This file is automatically generated by Android Tools.
+# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
+#
+# This file must be checked in Version Control Systems.
+#
+# To customize properties used by the Ant build system use,
+# "build.properties", and override values to adapt the script to your
+# project structure.
+
+# Project target.
+target=Google Inc.:Google APIs:11