Enhance 'summary' CLI command

[fraxken]

The goal would be to add a new command capable of outputting a summary from a JSON file. The summary would contain the same information as in the interface (excluding maintainers).

It would also include warnings statistics and an option to show the list of warnings (filterable by kind).

[tony-go]

hi @fraxken

In which format this summary could be? (pdf, jpg ?)

[targos]

I'd say it should be in the terminal.

[fraxken]

Ok a first version of the summary command has been merged in master. Any feedbacks are welcome.

All that's missing now is the warnings.