Checkpoint of data usage UI, graphs and lists.

Chart of network usage over time, with draggable "sweep" bars for
inspection region and warning/limits.  Talks with NetworkStatsService
for live data, and updates list of application usage as inspection
region changes.

Change-Id: I2a406e6776daf7d74143c07ec683c10fe711c277

src/com/android/settings/Settings.java

@@ -343,4 +343,5 @@ public class Settings extends PreferenceActivity implements ButtonBarHandler {
     public static class AccountSyncSettingsInAddAccountActivity extends Settings { }
     public static class CryptKeeperSettingsActivity extends Settings { }
     public static class DeviceAdminSettingsActivity extends Settings { }
+    public static class DataUsageSummaryActivity extends Settings { }
 }