* Add yarn.lock file for NodeServices
* Remove references to 'npm install' (causes double-download of node modules) and replace npm commands in package.json with yarn for consistency
* Upgrade yarn to 1.15.2
Part of #4246
Changes:
* Update source code layout to follow the new conventions for this repo
* Update project files to use `<Reference>`
* Update targets to build NPM packages
* Update BuildTools to support custom 'restore' and 'test' targets