Introduce fomantic-ui, replacing semantic-ui

Replaced semantic-ui with the drop-in replacement fomantic-ui [0]
which is a maintained fork. The fomantic-ui used here is a custom
build [1] of the less-version _without_ google-fonts (css-only). The
javascript part of fomantic-ui is not used, and also jquery could be
dropped now.

[0] https://fomantic-ui.com
[1] https://github.com/eikek/fomantic-slim-default

Issue: #349

modules/restserver/src/main/scala/docspell/restserver/webapp/TemplateRoutes.scala

@@ -138,12 +138,10 @@ object TemplateRoutes {
       IndexData(
         Flags(cfg),
         Seq(
-          "/app/assets" + Webjars.semanticui + "/semantic.min.css",
+          "/app/assets" + Webjars.fomanticslimdefault + "/semantic.min.css",
           s"/app/assets/docspell-webapp/${BuildInfo.version}/docspell.css"
         ),
         Seq(
-          "/app/assets" + Webjars.jquery + "/jquery.min.js",
-          "/app/assets" + Webjars.semanticui + "/semantic.min.js",
           "/app/assets" + Webjars.clipboardjs + "/clipboard.min.js",
           s"/app/assets/docspell-webapp/${BuildInfo.version}/docspell-app.js"
         ),