Listen for MY_PACKAGE_REPLACED broadcasts

* TODO: When the Intent arrives, resume any "running" alarm & notification.
* Android Studio also reformatted AndroidManifest.xml.
* Update the app_description string.
Fill in ResumeReceiver so it works

... actually resuming notifications and alarms.

Rename it from "UpgradeReceiver."
Tweak README.md
Increment to versionCode 11, versionName 2.1

Update to appcompat-v7 lib 21.0.2 and support-v4 lib 21.0.2.
Mostly handle reboot while running or paused

* If load() stops a "running" timer with a future startTime, then save() it
to ensure consistency.
* MainActivity start: update the widgets just in case.
* Add a long comment about reboot handling, including how to fix the
remaining corner case (at a cost).
shorter log msg
Use <plurals> for I18N.
Update screenshots for the text changes