ui: Initial Elm UI import

Merged from https://github.com/jhillyerd/inbucket-elm

Uses https://github.com/halfzebra/create-elm-app

ui/src/HttpUtil.elm

@@ -0,0 +1,39 @@
+module HttpUtil exposing (..)
+
+import Http
+
+
+delete : String -> Http.Request ()
+delete url =
+    Http.request
+        { method = "DELETE"
+        , headers = []
+        , url = url
+        , body = Http.emptyBody
+        , expect = Http.expectStringResponse (\_ -> Ok ())
+        , timeout = Nothing
+        , withCredentials = False
+        }
+
+
+errorString : Http.Error -> String
+errorString error =
+    case error of
+        Http.BadUrl str ->
+            "Bad URL: " ++ str
+
+        Http.Timeout ->
+            "HTTP timeout"
+
+        Http.NetworkError ->
+            "HTTP Network error"
+
+        Http.BadStatus res ->
+            "Bad HTTP status: " ++ toString res.status.code
+
+        Http.BadPayload msg res ->
+            "Bad HTTP payload: "
+                ++ msg
+                ++ " ("
+                ++ toString res.status.code
+                ++ ")"