Allow for defining profiles without sections

[kontur]

I may want to define a custom profile that is only a mix and match of other profiles and excluded checks, however a PROFILE definition requires a section. One can fake not defining sections like so, but this seems moot:

PROFILE = {
    "sections": {
        "": []
    },
…

If internally there is a need to have an (empty) section then the default for a PROFILE without defined sections should just be this mock empty value and allow the user to define profiles without explicit sections.

[kontur]

Equally, the configuration_defaults seem to be needed, but as far as I can tell all but one profile define this as the same:

"configuration_defaults": {
        "file_size": {
            "WARN_SIZE": 1 * 1024 * 1024,
            "FAIL_SIZE": 9 * 1024 * 1024,
        }
    },

Just allow omitting configuration_defaults and default to this. (A default for a default... maybe this is over-engineered?)

Or at the very least, the documentation here should mention what these entries expect.