ui: Initial Elm UI import

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

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

ui/src/Data/Metrics.elm

@@ -0,0 +1,62 @@
+module Data.Metrics exposing (..)
+
+import Json.Decode as Decode exposing (..)
+import Json.Decode.Pipeline exposing (..)
+
+
+type alias Metrics =
+    { sysMem : Int
+    , heapSize : Int
+    , heapUsed : Int
+    , heapObjects : Int
+    , goRoutines : Int
+    , webSockets : Int
+    , smtpConnOpen : Int
+    , smtpConnTotal : Int
+    , smtpConnHist : List Int
+    , smtpReceivedTotal : Int
+    , smtpReceivedHist : List Int
+    , smtpErrorsTotal : Int
+    , smtpErrorsHist : List Int
+    , smtpWarnsTotal : Int
+    , smtpWarnsHist : List Int
+    , retentionDeletesTotal : Int
+    , retentionDeletesHist : List Int
+    , retainedCount : Int
+    , retainedCountHist : List Int
+    , retainedSize : Int
+    , retainedSizeHist : List Int
+    }
+
+
+decoder : Decoder Metrics
+decoder =
+    decode Metrics
+        |> requiredAt [ "memstats", "Sys" ] int
+        |> requiredAt [ "memstats", "HeapSys" ] int
+        |> requiredAt [ "memstats", "HeapAlloc" ] int
+        |> requiredAt [ "memstats", "HeapObjects" ] int
+        |> requiredAt [ "goroutines" ] int
+        |> requiredAt [ "http", "WebSocketConnectsCurrent" ] int
+        |> requiredAt [ "smtp", "ConnectsCurrent" ] int
+        |> requiredAt [ "smtp", "ConnectsTotal" ] int
+        |> requiredAt [ "smtp", "ConnectsHist" ] decodeIntList
+        |> requiredAt [ "smtp", "ReceivedTotal" ] int
+        |> requiredAt [ "smtp", "ReceivedHist" ] decodeIntList
+        |> requiredAt [ "smtp", "ErrorsTotal" ] int
+        |> requiredAt [ "smtp", "ErrorsHist" ] decodeIntList
+        |> requiredAt [ "smtp", "WarnsTotal" ] int
+        |> requiredAt [ "smtp", "WarnsHist" ] decodeIntList
+        |> requiredAt [ "retention", "DeletesTotal" ] int
+        |> requiredAt [ "retention", "DeletesHist" ] decodeIntList
+        |> requiredAt [ "retention", "RetainedCurrent" ] int
+        |> requiredAt [ "retention", "RetainedHist" ] decodeIntList
+        |> requiredAt [ "retention", "RetainedSize" ] int
+        |> requiredAt [ "retention", "SizeHist" ] decodeIntList
+
+
+{-| Decodes Inbuckets hacky comma-separated-int JSON strings.
+-}
+decodeIntList : Decoder (List Int)
+decodeIntList =
+    map (String.split "," >> List.map (String.toInt >> Result.withDefault 0)) string