Summary:
- Moved /test/client and /test/common to core.
- Moved two files (CircularArray and RecentItems) from app/common to core/app/common.
- Moved resetOrg test to gen-server.
- `testrun.sh` is now invoking common and client test from core.
- Added missing packages to core's package.json (and revealed underscore as it is used in the main app).
- Removed Coord.js as it is not used anywhere.
Test Plan: Existing tests
Reviewers: paulfitz
Reviewed By: paulfitz
Subscribers: paulfitz
Differential Revision: https://phab.getgrist.com/D3590
