DATAJDBC-520 - Polishing.

Put the parts about references back.

Original pull request: #206.

Author: schauder

src/main/asciidoc/jdbc.adoc

@@ -271,7 +271,8 @@ public class MyEntity {
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-The {javadoc-base}org/springframework/data/relational/core/mapping/MappedCollection.html[`@MappedCollection`] annotation can be used on Sets, Lists, and Maps.
+The {javadoc-base}org/springframework/data/relational/core/mapping/MappedCollection.html[`@MappedCollection`]
+ annotation can be used on a reference type (one-to-one relationship) or on Sets, Lists, and Maps  (one-to-many relationship).
 `idColumn` element of the annotation provides a custom name for the foreign key column referencing the id column in the other table.
 In the following example the corresponding table for the `MySubEntity` class has a `NAME` column, and the `CUSTOM_MY_ENTITY_ID_COLUMN_NAME` column of the `MyEntity` id for relationship reasons: