Setup project for the new UI

We'd like to replace the existing UI with Angular + REST. Embed a new OWA in the new maven "owa" submodule, which is built using npm + webpack, but also can be built by maven as part of module's build using https://github.com/eirslett/frontend-maven-plugin. Use the yeoman generator to create a scaffolding for the OWA project.

Figure out a way to deploy the OWA when installing the module in OpenMRS. Ideally, we will deploy OWA only, if the Open Web Apps module is deployed.