Improve the startup sequence.

- new welcome dialog message.
- new check units text.
- for US and UK, default to imperial.
- for fragments, fix handling of onCancel. No need
  to handle onCancel at the dialog level.

MyTracks/src/com/google/android/apps/mytracks/io/fusiontables/SendFusionTablesAsyncTask.java

@@ -14,6 +14,7 @@ import com.google.android.apps.mytracks.stats.DoubleBuffer;
 import com.google.android.apps.mytracks.stats.TripStatisticsBuilder;
 import com.google.android.apps.mytracks.util.ApiAdapterFactory;
 import com.google.android.apps.mytracks.util.LocationUtils;
+import com.google.android.apps.mytracks.util.PreferencesUtils;
 import com.google.android.apps.mytracks.util.SystemUtils;
 import com.google.android.apps.mytracks.util.UnitConversions;
 import com.google.android.maps.mytracks.R;
@@ -32,7 +33,6 @@ import android.accounts.AccountManager;
 import android.accounts.AuthenticatorException;
 import android.accounts.OperationCanceledException;
 import android.content.Context;
-import android.content.SharedPreferences;
 import android.database.Cursor;
 import android.location.Location;
 import android.util.Log;
@@ -205,9 +205,7 @@ public class SendFusionTablesAsyncTask extends AbstractSendAsyncTask {
   private boolean uploadAllTrackPoints(Track track) {
     Cursor locationsCursor = null;
     try {
-      SharedPreferences prefs = context.getSharedPreferences(
-          Constants.SETTINGS_NAME, Context.MODE_PRIVATE);
-      boolean metricUnits = prefs.getBoolean(context.getString(R.string.metric_units_key), true);
+      boolean metricUnits = PreferencesUtils.isMetricUnits(context);
 
       locationsCursor = myTracksProviderUtils.getLocationsCursor(trackId, 0, -1, false);
       if (locationsCursor == null) {