for #950, update babel to v7 (#1077)

* for #950, upgrade babel to v7

* fix linting errors

* for #950, remove @babel/core from devDependencies (so it's only in dependencies) and change babel-loader config to use .babelrc

* for #950, changes to .babelrc to make  work

* for #950, include core-js modules in webpack config for IE support with babel/plugin-syntax-dynamic-import

* for #950, update babel and associated packages to LTS

Author: catarak