Fixes for the following issues, reviewed by neil_a_wilson.

Issue 785: attribute options not returned by search of attribute types only
Issue 786: SearchOperation#returnEntry does not always make a copy of the attributes

I have added some new methods so that a common code path can be followed whether the search returns attribute values or not.

Attribute:
   public Attribute duplicate(boolean omitValues)

Entry:
   public List<Attribute> duplicateUserAttribute(
        AttributeType attributeType,
        Set<String> options,
        boolean omitValues)

   public List<Attribute> duplicateOperationalAttribute(
        AttributeType attributeType,
        Set<String> options,
        boolean omitValues)