ui: Much elm work, such wow

- ui: Fix favicon
- webui: Changes to support serving Elm UI
- Static files now served from `/` mount point.
- Old UI handlers moved to `/serve` mount point, some will still be
  needed by the Elm UI; safe HTML and attachments for example.
- Update dev-start.sh for new UI, with tip on how to build it.
- ui: Detect browser host:port for websocket URL,
- webui: Remove unused mailbox handlers, rename routes
- Many routes not needed by Elm UI.
- `/serve/mailbox/*` becomes `/serve/m/*`.
- webui: Impl custom JSON message API for web UI,
- ui: Refactor Mailbox view functions,
- ui: Add body tabs for safe HTML and plain text,
- webui: Format plain text for new UI,
- ui: List attachments with view & download links,

ui/src/Main.elm

@@ -34,7 +34,7 @@ init : Value -> Location -> ( Model, Cmd Msg )
 init sessionValue location =
     let
         session =
-            Session.init (Session.decodeValueWithDefault sessionValue)
+            Session.init location (Session.decodeValueWithDefault sessionValue)
 
         model =
             { page = Home Home.init
@@ -197,7 +197,7 @@ setRoute route model =
             )
 
         Route.Monitor ->
-            ( { model | page = Monitor Monitor.init }
+            ( { model | page = Monitor (Monitor.init model.session.host) }
             , Ports.windowTitle "Inbucket Monitor"
             , Session.none
             )