fix: undefined configuration

[gentlementlegen]

Resolves #65

Depends on #68

[gentlementlegen]

Changes

This pull-request allows for the configuration to handle default and missing items within incentives so it becomes easier to set a configuration.

Supported values are:

incentives:

That would have all modules disabled (because none are present);

incentives:
    userExtractor: {}

To individually enable modules with their defaults;

incentives:
    githubComment:
        enabled: true
        post: true
        debug: false

to set values for a module.

QA run

Partially set configuration with defaults

[0x4007]

@gentlementlegen should this be closed?

[gentlementlegen]

@0x4007 I think this will close automatically when #68 goes in because it contains it, should be handled by GitHub.