Implement readProjectsFromRequest() helper for SearchEngines
Summary:
Ref T4100. This just makes the "specify stuff in query parameters" workflow a little better:
- You can now do `?projects=differential,diffusion`.
- You can now do `?projects=projects(alincoln)`.
Test Plan: Did that stuff ^^^^
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T4100
Differential Revision: https://secure.phabricator.com/D12468