Add a config with good DX

[KacperFKorban]

It should be possible to pass config options to GUInep. Those can either be front end specific or general GUInep options. e.g.

• flag that makes all non-nullable inputs as required
• an option to choose an alternative styling scheme

Some ideas for config:

• a given instance e.g.

  given GUInepConfig with
    override val useBananas: Boolean = true
  
  guinep.web(someTool)

• additional parameter list

  guinep.web(someTool)(useBananas = true)

• builder-ish (change web to be some guinep class instance with an apply method)

  guinep.web
    .withConfig(_.copy(useBananas = true))
    .apply(someTool)