[*] update babel
[client-app] remove flow-typed
[client-app] Move build/package.json to main package.json
[client-app] remove spec_integration
[client-app] fix babel support
Add client-private-plugins package.json
[client-app] add node_modules to global path for private-plugins
Move client-sync dependencies to client-app root
fix electron rebuild
[*] moved to monorepo
Summary: App now runs in monorepo
Test Plan: npm test
Reviewers: juan, mark, khamidou, halla, spang
Differential Revision: https://phab.nylas.com/D3947