First version of new ui based on tailwind

This drops fomantic-ui as css toolkit and introduces tailwindcss. With
tailwind there are no predefined components, but it's very easy to
create those. So customizing the look&feel is much simpler, most of
the time no additional css is needed.

This requires a complete rewrite of the markup + styles. Luckily all
logic can be kept as is. The now old ui is not removed, it is still
available by using a request header `Docspell-Ui` with a value of `1`
for the old ui and `2` for the new ui.

Another addition is "dev mode", where docspell serves assets with a
no-cache header, to disable browser caching. This makes developing a
lot easier.

modules/webapp/src/main/elm/Comp/StringListInput.elm

@@ -5,11 +5,13 @@ module Comp.StringListInput exposing
     , init
     , update
     , view
+    , view2
     )
 
 import Html exposing (..)
 import Html.Attributes exposing (..)
 import Html.Events exposing (onClick, onInput)
+import Styles as S
 import Util.Maybe
 
 
@@ -96,3 +98,50 @@ view values model =
                 []
             ]
         ]
+
+
+
+--- View2
+
+
+view2 : List String -> Model -> Html Msg
+view2 values model =
+    let
+        valueItem s =
+            div [ class "flex flex-row items-center" ]
+                [ a
+                    [ class S.deleteLabel
+                    , onClick (RemoveString s)
+                    , href "#"
+                    ]
+                    [ i [ class "fa fa-trash" ] []
+                    ]
+                , span [ class "ml-2" ]
+                    [ text s
+                    ]
+                ]
+    in
+    div [ class "flex flex-col" ]
+        [ div [ class "relative" ]
+            [ input
+                [ placeholder ""
+                , type_ "text"
+                , onInput SetString
+                , value model.currentInput
+                , class ("pr-10 py-2 rounded" ++ S.textInput)
+                ]
+                []
+            , a
+                [ href "#"
+                , onClick AddString
+                , class S.inputLeftIconLink
+                ]
+                [ i [ class "fa fa-plus" ] []
+                ]
+            ]
+        , div
+            [ class "flex flex-col space-y-4 md:space-y-2 mt-2"
+            , class "px-2 border-0 border-l dark:border-bluegray-600"
+            ]
+            (List.map valueItem values)
+        ]