Javadoc fixes in Versioned and TransactionManager

Change-Id: If4a8245aabfadaba15261aa3a4c90c6632cb73a3

@@ -91,6 +91,7 @@ public class Versioned<V> {
      * Maps this instance into another after transforming its
      * value while retaining the same version and creationTime.
      * @param transformer function to mapping the value
+     * @param <U> Versioned return type
      * @return mapped instance
      */
     public <U> Versioned<U> map(Function<V, U> transformer) {

@@ -59,6 +59,7 @@ public class TransactionManager {
      * Constructs a new TransactionManager for the specified database instance.
      *
      * @param database database
+     * @param mapBuilder map builder
      */
     public TransactionManager(Database database, ConsistentMapBuilder<Long, Transaction> mapBuilder) {
         this.database = checkNotNull(database, "database cannot be null");