Reana-client

- Adds support of wildcard patterns to `ls` command.
- Adds support of directory download and wildcard patterns to `download` command.
- Changes `list` command to include deleted workflows by default.
- Fixes environment image validation info message where UIDs were switched.

- Adds validation of workflow input parameters to the `validate` command.
- Adds optional validation of workflow environment images (`--environments`) to the `validate` command.

- Adds support for Python 3.9.
- Fixes exception handling when uploading files.
- Fixes minor code warnings.
- Fixes traling slash issue from user exported REANA_SERVER_URL.

- Changes `ping` command output to include REANA client and server version information.
- Fixes `upload` command to properly display errors.

- Adds option to `logs` command to filter job logs according to compute backend, docker image, status and step name.
- Adds new `restart` command to restart previously run or failed workflows.
- Adds possibility to specify operational options in the `reana.yaml` of the workflow.
- Fixes user experience by preventing dots as part of the workflow name to avoid confusion with restart runs.
- Changes `du` command output format.
- Changes file loading to optimise CLI performance.
- Changes `logs` command to enhance formatting using marks and colours.
- Changes from Bravado to requests to improve download performance.
- Changes `ping` command to perform user access token validation.
- Changes defaults to accept both `reana.yaml` and `reana.yml` filenames.
- Changes `diff` command to improve output formatting.
- Changes code formatting to respect `black` coding style.
- Changes documentation to single-page layout.

- Fixes installation troubles for REANA 0.6.x release series by pinning several
dependencies.