Update javadocs.

bramble-android/src/main/java/org/briarproject/bramble/api/system/AndroidWakeLockManager.java

@@ -7,9 +7,21 @@ import java.util.concurrent.Executor;
 @NotNullByDefault
 public interface AndroidWakeLockManager {
 
+	/**
+	 * Creates a wake lock with the given tag. The tag is only used for
+	 * logging; the underlying OS wake lock will use its own tag.
+	 */
 	AndroidWakeLock createWakeLock(String tag);
 
+	/**
+	 * Runs the given task while holding a wake lock.
+	 */
 	void runWakefully(Runnable r, String tag);
 
+	/**
+	 * Submits the given task to the given executor while holding a wake lock.
+	 * The lock is released when the task completes, or if an exception is
+	 * thrown while submitting or running the task.
+	 */
 	void executeWakefully(Runnable r, Executor executor, String tag);
 }