Port LdapTemplate CRUD operations

`LdapTemplate` includes support for ODM. Instead of porting this over to `LdapClient`, it's worth considering placing it into something that follows the Spring Data model like so:

```java
public class SpringLdapRepository<T> {
    private final LdapClient client;
    private final ObjectMappingDirectory odm = ...;

    public List<T> findAll() { 
        // ...
    }
}
```