Upload plugin throws NotImplementedError for filetype 'symlink'

The Upload plugin needs support for 'symlink' file types. A way to detect remote filesystem type/symlink support would be preferable, otherwise it should warn the user of the symlinks that will not be uploaded.

Temporarily, I modified __init__.py as follows:

[in def upload_full_tree @line 447]:
...
elif ie.kind == 'directory': #existing
    self.make_remote_dir_robustly(relpath)
elif ie.kind == 'symlink': #new
    self.upload_file_robustly(relpath, ie.file_id)
...

This modification does not address other functions where the 'symlink' file type may appear, such as UploadTree. The modification also assumes that the receiving filesystem can handle symlinks correctly.