Prepare to have several helloweb programs each written in its own
language, and installed into bin/ as helloworld-<language> and exposed
as separate service to the web on its own port.

For component/helloweb we just rename installed script and section.

For software/helloworld we split helloweb & helloweb-promise section
into base and generate requested helloweb-<kinds> & friends via jinja2
programming; the same for exposing url for each kind.

So far it is only preparatory changes for new kinds - i.e. instance code
now supports it, but the only kind so far is still python.

/cc @jerome