(core) Moving client and common tests to core

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

.gitignore

@@ -50,6 +50,7 @@ build/Release
 # Dependency directories
 /node_modules/
 jspm_packages/
+/docs
 
 # Optional npm cache directory
 .npm