Refactor the whole configuration

Reviewed-on: #1

modules/nixos/multimedia/web/firefox/preferences.nix

@@ -0,0 +1,23 @@
+let
+  prefToString = value:
+    if builtins.isBool value then
+      if value then "true" else "false"
+    else if (builtins.isInt value) || (builtins.isNull value) then
+      builtins.toString value
+    else if builtins.isString value then
+      ''"${value}"''
+    else
+      builtins.throw
+        "Pref expected one of (Bool, String, Int, Null) got instead ${builtins.typeOf value}";
+
+  mkPrefs = prefs: builtins.concatStringsSep 
+    "\n"
+    (builtins.attrValues
+      (builtins.mapAttrs
+        (n: v: ''pref("${n}", ${prefToString v});'') prefs));
+in 
+  mkPrefs {
+    "browser.urlbar.suggest.topsites" = false;
+    "browser.startup.homepage" = "about:blank";
+    "browser.download.useDownloadDir" = false;
+  }