code "constructive dilemma"

[MichaelHoffmann]

There is a picture of the scheme in one of the comments to issue #204

It should be available

• to defend the enabler of a disjunctive syllogism (see issue #204)
• in the beginning of a mapping process when user selects "or do you want to start with an argument scheme?"
• when user selects "create a map from a template."

Adding further reasons (expanding) the constructive dilemma is described in a comment to issue #204.