Minor fixes to solve some compilation warnings

Missing version for compiler, javadoc, source and deploy plugin in POM was
causing some warning messages during the compilation with Maven.

In addition, the Javadoc was fixed in the OwnerService and PetService
classes.

pom.xml

@@ -62,6 +62,10 @@
 
 		<!-- Plugins versions -->
 		<wildfly.maven.plugin.version>1.1.0.Alpha4</wildfly.maven.plugin.version>
+		<maven.compiler.plugin.version>3.3</maven.compiler.plugin.version>
+		<maven.source.plugin.version>2.4</maven.source.plugin.version>
+		<maven.javadoc.plugin.version>2.10.3</maven.javadoc.plugin.version>
+		<maven.deploy.plugin.version>2.8.2</maven.deploy.plugin.version>
 		<maven.dependency.plugin.version>2.10</maven.dependency.plugin.version>
 		<maven.surefire.plugin.version>2.18.1</maven.surefire.plugin.version>
 		<maven.resources.plugin.version>2.7</maven.resources.plugin.version>
@@ -243,6 +247,26 @@
 		</plugins>
 		<pluginManagement>
 			<plugins>
+				<plugin>
+					<groupId>org.apache.maven.plugins</groupId>
+					<artifactId>maven-compiler-plugin</artifactId>
+					<version>${maven.compiler.plugin.version}</version>
+				</plugin>
+				<plugin>
+					<groupId>org.apache.maven.plugins</groupId>
+					<artifactId>maven-javadoc-plugin</artifactId>
+					<version>${maven.javadoc.plugin.version}</version>
+				</plugin>
+				<plugin>
+					<groupId>org.apache.maven.plugins</groupId>
+					<artifactId>maven-source-plugin</artifactId>
+					<version>${maven.source.plugin.version}</version>
+				</plugin>
+				<plugin>
+					<groupId>org.apache.maven.plugins</groupId>
+					<artifactId>maven-deploy-plugin</artifactId>
+					<version>${maven.deploy.plugin.version}</version>
+				</plugin>
 				<plugin>
 					<groupId>org.apache.maven.plugins</groupId>
 					<artifactId>maven-dependency-plugin</artifactId>

service/src/main/java/es/uvigo/esei/xcs/service/OwnerService.java

@@ -90,6 +90,7 @@ public class OwnerService {
 	 * Updates a new owner. If the owner is not stored, it will be persisted.
 	 * 
 	 * @param owner an owner to be updated.
+	 * @return the updated owner.
 	 * @throws IllegalArgumentException if {@code owner} is {@code null}.
 	 */
 	public Owner update(Owner owner) {

service/src/main/java/es/uvigo/esei/xcs/service/PetService.java

@@ -89,7 +89,8 @@ public class PetService {
 	 * Updates the information of a pet. If the pet is not stored, it will be
 	 * created.
 	 * 
-	 * @param pet a pet to be updated. 
+	 * @param pet a pet to be updated.
+	 * @return the updated pet.
 	 * @throws IllegalArgumentException if the pet has no owner.
 	 * @throws EJBAccessException if the pet's owner is not the current user.
 	 */