Add config.js, gruvbox.css, debug panel dropdowns

config.js

@@ -0,0 +1,12 @@
+/* Application configuration
+ * debug      - Show debug panel (0/1)
+ * theme      - Color palette: 'ash' or 'gruvbox'
+ * units      - Measurement units: 'metric' or 'imperial'
+ * language   - UI language: 'de' or 'en'
+ */
+window.CONFIG = {
+    debug: 1,
+    theme: 'ash',
+    units: 'metric',
+    language: 'de'
+};