feature: redirect to webapp by displayName

[tkurki]

Signal K webapps have displayName property. This PR adds automatic redirect to that webapp when the server's root is accessed with a hostname whose first element is the webapp's displayName.

So if you have a webapp whose displayName is foo and you access the server using url like http://foo.bar.org:3000/ you will be redirected to that webapp instead of the default landingPage that is the Admin webapp.

[tkurki]

Here's an idea to create shortcuts to webapps via specially crafted hostnames. Could downstream systems like OpenPlotter create freeboard-sk.local type aliases to facilitate this? Thoughts @panaaj @sbender9 @godind

[cmotelet]

By changing the hostname, the webapp will lose what it has stored in the browser's local storage ?

[tkurki]

Authentication will not work either across hosts without additional tweaking.

[tkurki]

...but I don't see localstorage as a problem, if you use one address consistently.

[panaaj]

Changing the display name, although not likely to occur often will also cause the issue.

It's just comes down to managing the change over when it occurs, that will be the trigger for preferences in local storage to be lost.
Of course if they are stored on the server as well then the impact is lessened.