* Add interval class
* Take dependency as const reference
* Compute forbidden intervals for ule-constraints
* Add class for evaluated interval
* We need the evaluated bounds as well
* Don't add constraint to cjust multiple times (hack, to be improved later)
* typo
* More interval helpers
* Add constraint::ult factory function
* Fix forbidden interval condition
* Add solver::has_viable
* Add conflict explanation using forbidden intervals (not yet fully integrated into solver)
