Add support for demo mode in docker. roundup/demo.py Make changes to allow exposed port in docker to be specified separately from the port that demo mode binds to. Also permit bind address specification as well. roundup/scripts/roundup_demo.py: Update required by changes in demo.py. Also move away from positional arguments to prefer flag arguments. Required for passing port and host specification. Flake8 fixes. share/man/man1/roundup-demo.1 Document use of option flags rather than positional params. Other cleanups. doc/installation.txt: Document new docker modes: demo, shell and admin. Update docs: overview section - reorg, added template info for the impatient section - added docker demo mode reference, more docs on top level demo.py use. new section on docker demo mode removed getting roundup section. folded into installing roundup. also prior for the impatient section describes how to download. install via pip in venv recommended supported method document all provided templates. not just minimal and classic. added index references. move sections around, decreased sectin depth, reformatting scripts/Docker/roundup_healthcheck: When running roundup-demo, there is no tracker spec. So default to demo if no tracker=directory args found. Prevent's docker from reporting an unhealthy container when running demo. scripts/Docker/roundup_start: implement demo, shell, admin docker modes.

class MockNull:
    def __init__(self, **kwargs):
        for key, value in kwargs.items():
            self.__dict__[key] = value

    def __call__(self, *args, **kwargs): return MockNull()
    def __getattr__(self, name):
        # This allows assignments which assume all intermediate steps are Null
        # objects if they don't exist yet.
        #
        # For example (with just 'client' defined):
        #
        # client.db.config.TRACKER_WEB = 'BASE/'
        self.__dict__[name] = MockNull()
        return getattr(self, name)

    def __getitem__(self, key): return self
    def __bool__(self): return False
    # Python 2 compatibility:
    __nonzero__ = __bool__
    def __contains__(self, key): return False
    def __eq__(self, rhs): return False
    def __ne__(self, rhs): return False
    def __str__(self): return ''
    def __repr__(self): return '<MockNull 0x%x>'%id(self)
    def gettext(self, str): return str
    _ = gettext
    def get(self, name, default=None):
        try:
            return self.__dict__[name.lower()]
        except KeyError:
            return default