Maniphest - allow for searching for tasks based on dependency relationships
Fixes T5352. This is very useful for finding things that should be easy to do ("not blocked") as well as things that are important to do ("blocking"). I have wanted to check out the latter case in our installation, though no promises on what I would end up actually doing from that search result list. =D
I also think supporting something like T6638 is reasonable but the UI seems trickier to me; its some sort of task tokenizer, which I don't think we've done before?
Test Plan: toggled various search options and got reasonable results. When i clicked conflicting things like "blocking" and "not blocking" verified it was like I had not clicked anything at all.
Reviewers: chad, epriestley
Reviewed By: epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T5352
Differential Revision: https://secure.phabricator.com/D11306