Allow foregrounding of the server process (see #12281).

This PR adds a new CLI parameter (``-fg`` or ``--foreground``) that will force the server to run in foreground and not create a daemon (or Windows service on Windows). The terminal in which the ``bin\omero admin start -fg`` command is run will be blocked for the lifetime of the server. To stop the server, use the (Cmd | Ctrl) + C key combination.

Also, the JVM parameters for remote debugging in ``templates.xml`` have been updated to a more recent syntax.

To test:
- see that the new option does what it promises,
- check that remote debugging still works (for developers only).

@joshmoore Have you ever tried using ``iceserviceinstall`` on Windows to create the OMERO.master Windows service? It seems we could avoid some of the PyWin32 deps if that would be a working solution.