Merge klighd-core and klighd-interactive back into a single package

[NiklasRentzCAU]

The separation of klighd-core and klighd-interactive leaves a unwanted dependency direction in the system: the core depends on one specific feature (the interactive stuff), which should be the other way around. Either klighd-core should be more extensible to allow the dependency to reverse so that klighd-interactive can hook into the core directly or the interactive code should just be a sub-folder next to the other features in klighd-core.

This would also have the benefit, that we do not need all the duplicate definitions of the KGraph structure anymore, or the KGraph structure not being defined in the core, but in the interactive package.