feat(tools): Add more commands to package.json

[vladitasev]

This change exposes two more nps commands as package scripts: serve and watch, and additionally enhances the test command.

Examples:

Command	What it does
yarn test	Runs the dev server and executes all tests
yarn test --no-server	Executes all tests only
yarn test test/specs/Button.spec.js	Executes a single spec only (does not run server, no changes)
yarn serve	Runs the test server only
yarn watch	Runs the watch utility only
yarn watch test	Only watches for changes in the test files
yarn watch src	Only watches for changes in the source files
yarn watch templates	Only watches for template changes

This granularity would allow package authors greater flexibility, f.e. they could combine:

• yarn serve
• yarn test --no-server
• yarn watch test
  arbitrarily based on specific use-cases.

related to: #1767