GOSSIP-81 Move Jackson and UDP to their own modules

Part of what makes this work is the test implementation of TransportManager.

This PR is pretty straightforward. A few gotchas though:
* A message signing test was moved into `JacksonTests` because that is
  where the signing actually happens.
* A CRDT serializing test was moved there as well. It's the best place
  for now.
* No UDP tests at all. I plan to fix that in a bit. Reasoning is that it is
  difficult to test any TransportManager implementation without bring up
  a full stack. I plan to address this in the future (GOSSIP-83).
* Simple round trip Jackson serialization tests.

pom.xml

@@ -56,6 +56,8 @@
 	
 	<modules>
 		<module>gossip-base</module>
+		<module>gossip-transport-udp</module>
+		<module>gossip-protocol-jackson</module>
 	</modules>
 	
 	<description>A peer to peer cluster discovery service</description>
@@ -81,6 +83,39 @@
 		<url>https://issues.apache.org/jira/browse/GOSSIP</url>
 	</issueManagement>
 	
+	<dependencies>
+		<dependency>
+			<groupId>org.junit.jupiter</groupId>
+			<artifactId>junit-jupiter-api</artifactId>
+			<version>${junit.jupiter.version}</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.junit.jupiter</groupId>
+			<artifactId>junit-jupiter-engine</artifactId>
+			<version>${junit.jupiter.version}</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.junit.vintage</groupId>
+			<artifactId>junit-vintage-engine</artifactId>
+			<version>${junit.vintage.version}</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.junit.platform</groupId>
+			<artifactId>junit-platform-runner</artifactId>
+			<version>${junit.platform.version}</version>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>io.teknek</groupId>
+			<artifactId>tunit</artifactId>
+			<version>${tunit.version}</version>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+	
 	<build>
 		<pluginManagement>
 			<plugins>