Add client submodule, change config to set webapp directory to client directory

Client submodule was added so that heroku release will include the client.
configuration tag added to pom.xml sets webapp directory to clients directory. If there is no client submodule and no client directory it will complain and default to default directory containing index.html. Contents of this will be API description in the future when stable.
Change client submodule address to publicly accessible one
Add resourceBase to main