Store schema version in database. Dev task #50.

If the schema of the database is incompatible with the schema expected
by the code, the database throws a DbSchemaException. LifecycleManager
indicates the error to BriarService, which uses HomeScreenActivity to
show a notification and quit the app.

briar-tests/src/org/briarproject/TestLifecycleModule.java

@@ -17,7 +17,7 @@ public class TestLifecycleModule extends AbstractModule {
 
 			public void registerForShutdown(ExecutorService e) {}
 
-			public void startServices() {}
+			public boolean startServices() { return true; }
 
 			public void stopServices() {}