Refactor Calendar Search, and implement Projects on events

Summary: Ref T7950, Refactor Calendar Search, and implement Projects on events

Test Plan: Verify that all queries in Calendar search still work, and that events can now have associated Projects that you can search by in Calendar Search.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T7950

Differential Revision: https://secure.phabricator.com/D13393