### Summary
- Cleans up target cancellation being called incorrectly.
- An invalid target type (which should never happen), now calls `OnTargetUntargetable` instead of `OnTargetCanceled`
- Removes double calls to `FinishSequence` in Spells.
- [X] `BaseRegion.CheckTravel` now properly cascades through parent regions
- [X] `SpellHelper.CheckTravel` now returns a failure message instead of sending one internally.
- [X] Consolidates travel restriction messages so they aren't duplicated.
