Issue 27 - Add a module for working with dse.ldif file
    
    Description: For some tests we need a way to parse and edit dse.ldif
    file. For starters, it will be nice to have next operations support:
    - get - Return attribute values under a given entry;
    - add - Add an attribute under a given entry;
    - delete - Delete singlevalued or multivalued attributes under a given entry;
    - replace - Replace attribute values with a new one under a given entry.
    
    Add tests to lib389/tests/dseldif_test.py
    
    https://pagure.io/lib389/issue/27
    
    Reviewed by: wibrown (Thanks!)