Herald - add ability to conditionalize on Maniphest Task projects

Summary: adds FIELD_PROJECTS and deploys it to Maniphest Task Herald Adapter. Went with "projects" because it feels like that could go well in other Adapters that want to conditionalize based on project.

Test Plan: made a new herald rule to be cc'd if project foo was on a task. it worked!

Reviewers: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7564