add Example in cobra commands definitions

[feloy]

Cobra Commands support an Example field, to display examples of the command when the help of the command is displayed.

Let's add meaningful examples to the different commands:

• init
• workspace list
• workspace remove

Test the examples using unit tests:

Consider the Example string:

# List all workspaces (human-readable format):
kortex-cli workspace list

# List all workspaces using short alias (human-readable format):
kortex-cli list

# List workspaces in JSON format
kortex-cli workspace list --output json

• extract from this string the commands (ignore empty lines and lines starting with #, consider lines starting with kortex-cli, and fail if other lines exist)
• analyze the command line, and check that:
  • the command and subcommands exist
  • the flags are supported

Aliases commands will inherit Example from their original command, by replacing the original command with the alias