Add ability to lock relationships to never be culled

@xochiquetzl_xkvn Yes I had a situation where I had a University Professor with a second wife and estranged adult kids. He had another daughter from an affair and I had one half brother find her and try to build a relationship, she's a soldier and he's a cop. When he travelled with his brothers to introduce them to her, he'd forgotten her. I had them building an awkward slow friendship and it wasn't high enough so it went back to strangers.
They kept forgetting their dad too because they weren't speaking to him, I mean he'd been a bit of a dog lol and it caused a rift. But they'd been created from the same household so should have known each other.