Add a features command to display available features

[bhermann]

Is your feature request related to a problem? Please describe.
Command-line users currently need to guess feature names. Or use the retrieve command to get a list.

Describe the solution you'd like
Add a features command that lists the available features and their descriptions.
Refers to delphi-hub/delphi-webapi#30

Describe alternatives you've considered
none

Additional context
none