COLLECTION Improvements to copy functions
    
    This patch adds better options for
    copying collections in flat mode.
    It allows caller of the interface
    to control prefixing of the fields
    when one collection is appended to another.
    It also avoids creating prefixes when the
    collection is simply copied in flat mode.
    Also for ELAPI I realized that the most efficient
    way to deal with the "resolved" event
    (event where all templeted values are actually replaced
    with the real values) is to add a callback
    capability to a copy collection function
    so that the callback can be used to modify
    the data (resolve it) while the copy operation
    is in progress. This approach eliminates the need
    for separate set of lookups after the event
    is already copied.