Add --help-all CLI

[davidbrochart]

Closes #71

@agronholm what do you think about doing something like that, where the configuration is printed as a side effect of running the application? I guess there is no way to "inspect" the application structure and gather all components' configuration without actually creating the resources, right?
This will show something like:

$ my_app --help-all
Container0 (components: 'dict[str, dict[str, Any] | None] | None' = None) -> 'None'
Container0.container1 (components: 'dict[str, dict[str, Any] | None] | None' = None) -> 'None'
Container0.container2 (components: 'dict[str, dict[str, Any] | None] | None' = None) -> 'None'
Container0.container1.dummy (dummyval1=None, dummyval2=None)
Container0.container2.dummy (dummyval1=None, dummyval2=None)

[coveralls]

coverage: 97.346%. first build
when pulling ee5ef40 on davidbrochart:help-all
into c879016 on asphalt-framework:master.

[agronholm]

I'm not sure about this. I had been thinking of a different configuration system that would allow both documenting and validating the configuration. Switching to that would require refactoring this option too, and I think it should be renamed regardless. One other thing: I don't like the hackish implementation either. Perhaps this should be deferred until there's a better config system?

[davidbrochart]

Sure, no problem. I'm thinking I could also have a component that would be added to the CLIApplicationComponent and that would inspect the child components to achieve the same behavior as in this PR. At least it would be external to Asphalt core.