Fixes some JavaDoc errors

Some JavaDoc errors detected in the entities have been fixed.

domain/src/main/java/es/uvigo/esei/xcs/domain/entities/Owner.java

@@ -79,9 +79,8 @@ public class Owner extends User implements Serializable {
 	}
 	
 	/**
-	 * Returns the pets that belongs to this owner. The collection returned is
+	 * Returns the pets that belong to this owner. The collection returned is
 	 * unmodifiable and no order are guaranteed.
-	 * If the pet already belongs to this owner, no action will be done.
 	 * 
 	 * @return the pets that belongs to this owner. 
 	 */
@@ -138,6 +137,8 @@ public class Owner extends User implements Serializable {
 	/**
 	 * Adds a pet directly to the pets collection of this owner if the pet does
 	 * not already belongs to this owner. The pet's owner will not be updated.
+	 * If the pet already belongs to this owner, no action will be done.
+	 * 
 	 * 
 	 * @param pet the pet to add to this owner. {@code null} values not
 	 * supported.

domain/src/main/java/es/uvigo/esei/xcs/domain/entities/Pet.java

@@ -103,6 +103,11 @@ public class Pet implements Serializable {
 		this.setOwner(owner);
 	}
 	
+	/**
+	 * Returns the identifier of this pet.
+	 * 
+	 * @return the identifier of this pet. 
+	 */
 	public int getId() {
 		return id;
 	}
@@ -195,7 +200,7 @@ public class Pet implements Serializable {
 	}
 
 	/**
-	 * Sets the owner of this pet. The new owner can be {@code null}, meaining
+	 * Sets the owner of this pet. The new owner can be {@code null}, meaning
 	 * that the pet has no owner.
 	 * 
 	 * @param owner the new owner of the pet. {@code null} value is valid,

rest/src/main/java/es/uvigo/esei/xcs/rest/OwnerResource.java

@@ -119,6 +119,7 @@ public class OwnerResource {
 	 * Deletes an owner.
 	 * 
 	 * @param login the login of the owner to be deleted.
+	 * @return an empty {@code OK} response.
 	 * @throws IllegalArgumentException if {@code login} is {@code null} or if
 	 * it does not identifies a valid owner.
 	 */

rest/src/main/java/es/uvigo/esei/xcs/rest/PetResource.java

@@ -129,6 +129,7 @@ public class PetResource {
 	 * Deletes a pet.
 	 * 
 	 * @param id the identifier of the pet to be deleted.
+	 * @return an empty {@code OK} response.
 	 * @throws IllegalArgumentException if there is no pet with the provided
 	 * identifier.
 	 * @throws SecurityException if the pet's owner is not the current user.