support SQL arrays

Both Hibernate and EclipseLink have an `@Array` annotation for mapping Java arrays to SQL `array` types.

I therefore think we should add the following annotation to JPA:

```java
@Target({FIELD, METHOD})
@Retention( RUNTIME )
public @interface Array {
/**
* The maximum length of the array.
*/
int length();
}
```

You could use it like this:

```java
@Array(length=10)
String[] tags;
```

Start by reviewing how JPA currently represents database array types and how Hibernate and EclipseLink expose their @Array annotations. Define the required JPA mapping behavior and integration points, then verify that the proposed annotation supports the shown String[] example and has compatible specification coverage.

Written by the indexing model from the issue text.