LP#1739803 Webstaff: Replace Grunt with Webpack

LP#1739803 Webstaff: Replace Grunt with Webpack

* Remove grunt devDependencies
* Add Webpack devDepenencies
* Copy and minify operations are now handled by Webpack via 'npm run
  build' for dev builds and 'npm run build-prod' for
  production/minified builds.
* Running 'npm run build-watch' executes webpack in --watch mode to
  watch for affected file changes and automatically rebuild.  Useful for
  development.
* Karma unit tests are now invoked directly from node via 'npm run
  test'.
* Docs and release installer updated to match.
* Removed long-outdated inline installer readme.

Webpack is configured to create bundles from sets of JS files.  As it
stands, there are 2 sets: core.bundle.js and vendor.bundle.js.  Core has
all of the EG core services that are loaded on every page.  Vendor
contains all of the 3rd-party dependencies (angular, etc.).  These 2
bundles are loaded on every web staff page (via base_js.tt2).

All other <script/> tags remain as they were.

When building in dev mode ('npm run build'), JS files are bunded,
un-minified, with an inline source map for debugging.

Signed-off-by: Bill Erickson <berickxx@gmail.com>