Bug 555955 - Allow CoS values to be merged
    
    This patch adds the ability for CoS values to be merged and create
    multi-valued attributes.  One can append "merge-schemes" the the
    end of the cosAttribute value in a definition entry to allow values
    to be merged.
    
    With a single indirect CoS definition, a merge will make CoS use
    each specifier attribute value in the target entry to look for
    CoS values in each of the found template entries.  All of these
    values will then be applied to the target entry (with the exception
    of duplicate values).
    
    With multiple indirect CoS definitions for the same attribute,
    setting merge mode for all definitions will cause all of the
    definitions to be used to find the values to apply to the target
    entry.  If merge-schemes is not defined for all of these definitions,
    the result is undefined (values from the first found CoS definition
    will be applied).