Switch buildTools, SDK, & support libs from 19 to 21

This brings in some of the "material design" appearance and enables Android
Lollipop (Android 5.0, API v21) SDK features.

* Replace an unknown android:background resource ref which the new tools
rejected.
* Change build.gradle to "plugin: 'com.android.application'" since plain
'android' is deprecated by the new tools.
* Increment the app's versionCode to 9 and versionName to "1.2".
Use support.v4 API level 21 Notification*Compat

+ NotificationManagerCompat
+ .setCategory(CATEGORY_ALARM)
+ .setVisibility(NotificationCompat.VISIBILITY_PUBLIC

So the OS displays the notification details on the lock screen and
and categorizes it for ranking and filtering.
Adjust the Start/Reset bar bg color

to work better in Material & Holo Light & Dark themes.
Get the pause action into the Lollipop lock screen notification.

This required working around Issue 1659, "There is no NotificationCompat.MediaStyle in the support library".
Refactor the MediaStyle workaround

to eliminate the duplicate application code and make it easy to remove the
workaround if/when NotificationCompat supports MediaStyle.