[XrdCl] Implement property list
[XrdClTests] Test PropertyList
[XrdCl] Allow all statuses to carry a message
[XrdCl] Add an util to print a PropertyList
[XrdCl] Refactor CopyProcess to use PropertyList
[XrdCl] Move xrdcopy to the new API
[XrdCl] Make checksum printing format the same as xrdcp