client: build workspace services using gulp

Rename `scripts/modules/common/workspace.js` to `workspace.services.js`
to make it consistent with other source files providing services.

Add a gulp build task to generate the services file using
loopback-sdk-angular.

Remove `workspace.services.js` from version control, as it is
auto-generated now.
client: remove style.css from version control

This file is generated by `gulp build-less`.