Added eslint to resource-manager project and updated dnn-elements to latest

[valadas]

In https://github.com/DNNCommunity/dnn-elements/tree/develop/packages/stencil-library/eslint-plugin I implemented our own eslint plugin that will help manage future deprecations/best-practices regarding dnn-elements.

This PR adds eslint to the resource-manager project and then updated dnn-elements to the latest and uses those rules. I also refactored a lot of code from using Promises to use async/await which is much more readable and understandable.