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.

SignalStrengthSampler/proguard.cfg

@@ -0,0 +1,34 @@
+-optimizationpasses 5
+-dontusemixedcaseclassnames
+-dontskipnonpubliclibraryclasses
+-dontpreverify
+-verbose
+-optimizations !code/simplification/arithmetic,!field/*,!class/merging/*
+
+-keep public class * extends android.app.Activity
+-keep public class * extends android.app.Application
+-keep public class * extends android.app.Service
+-keep public class * extends android.content.BroadcastReceiver
+-keep public class * extends android.content.ContentProvider
+-keep public class com.android.vending.licensing.ILicensingService
+
+-keepclasseswithmembernames class * {
+    native <methods>;
+}
+
+-keepclasseswithmembernames class * {
+    public <init>(android.content.Context, android.util.AttributeSet);
+}
+
+-keepclasseswithmembernames class * {
+    public <init>(android.content.Context, android.util.AttributeSet, int);
+}
+
+-keepclassmembers enum * {
+    public static **[] values();
+    public static ** valueOf(java.lang.String);
+}
+
+-keep class * implements android.os.Parcelable {
+  public static final android.os.Parcelable$Creator *;
+}