[typescript-angular] Update default Angular version from 4.3 to 7.0 (NPM Client)

Created by: karismann

Angular 4.0.0 LTS ended on September 23, 2018. It should be safe now to upgrade the default Angular build version to the latest major version (7.0.0).

Upgrading would also prevent people who use Angular >= 6.0 can't get a working package without adding --additional-properties ngVersion=7 to the generate script.