Include zanata-editor in the frontend maven module.
- it can still have a separate package.json and be in a separate subdirectory (i.e. it can be a separate npm module)
- able to build just the npm module that you are working on without having to wait for unrelated parts to build
- mvn package should build all the jar files
- can be a single jar with all the npm modules under frontend, or separate jars (whichever makes most sense).