Added python skript for getting files from dcache, merging and moving to net_scratch
Added check for the list of the copied files in the merge script
Rearranged fileRetriever script code.
Added some safety measures after executing the shell commands.
In this version, really execute the commands
Bugfix: Define DEVNULL globally
Added an option to give a custom list of files for merging
Bugfix: For rm cmd remove 'file:' in front of files listed for merging
Added check for copying whether file already exists locally.