Merge branch 'validation-hooks' into 'master'

Run hooks when messages are validated

This patch allows clients to respond to messages reliably. Like the hooks for adding/removing contacts/identities, these hooks may be run more than once - that will be fixed when we have client-layer transactions.

See merge request !95

briar-tests/src/org/briarproject/sync/ValidationManagerImplTest.java

@@ -0,0 +1,14 @@
+package org.briarproject.sync;
+
+import org.briarproject.BriarTestCase;
+import org.junit.Test;
+
+import static org.junit.Assert.fail;
+
+public class ValidationManagerImplTest extends BriarTestCase {
+
+	@Test
+	public void testUnitTestsExist() {
+		fail(); // FIXME: Write tests
+	}
+}