cli: upload wrapper command

[tiborsimko]

REANA-Client needs an argument which files to upload:

$ reana-client upload --help
Usage: reana-client upload [OPTIONS] FILE(s)

  Upload one of more files to the workflow workspace.

Options:
  -w, --workflow TEXT      Name or UUID of the workflow you are uploading
                           files for. Overrides value of $REANA_WORKON.
  -t, --access-token TEXT  Access token of the current user.
  --help                   Show this message and exit.

Let us provide an option to upload all files/directories specified in reana.yaml, for example:

$ reana-client upload --all

or even:

$ reana-client upload

so that if no arguments are given, the files to upload are read from reana.yaml.