file logging now always show the $original_file_path, not the shadow path.

added $original_file_path variable
fixed backups without shadow drive
file logging now always show the $original_file_path, not the shadow
path.
function get-longchilditem added: it is used instead of get-childitem to
seek for paths and files which are to be copied. This is because
get-childitem doesn't support long paths, so we use robocopy as the
underlying system.
shorten_path slightly adjusted to allow recursion.
:MainLoop extended for use with get-longchilditem.
little adjustment of the shadow creation process
$ExclusionList is now $ExclusionFile

$exclusion_file removed
litttle explanation added in shorten path function