--help does not list commands

Issuing `s4cmd --help` yields `Usage: s4cmd [options]` and lists a lot of options, but implies that there are only options, no commands:

```
$ s4cmd --help
Usage: s4cmd [options]

Super S3 command line tool. Version 2.1.0

Options:
...
```

Still unsurprisingly just running `s4cmd` with all optional options omitted will yield `[Invalid Argument] No command provided` so the documentation printed with `--help` is wrong on that regard:

```
$ s4cmd
[Invalid Argument] No command provided
```

This is inconsistent and forces the user to look up the commands on the internet since the man page just reproduces the incomplete/wrong information of the `--help` option.

In my opinion the `--help` option and the man page should list all command listed in the `README.md`, so this tool becomes usable without having to look up the source repository first.

Read README.md to identify the complete command list, then locate the sources for the --help output and the man page. Update both displays so they list the commands documented in README.md, and verify that `s4cmd --help` no longer implies the tool accepts only options.

Written by the indexing model from the issue text.