Added language and theme settings.

lang/en-US.json

@@ -28,6 +28,7 @@
   "label.enable-share-url": "Enable share URL",
   "label.invalid": "Invalid",
   "label.invalid-domain": "Invalid domain",
+  "label.language": "Language",
   "label.last-days": "Last {x} days",
   "label.last-hours": "Last {x} hours",
   "label.logged-in-as": "Logged in as {username}",
@@ -50,6 +51,7 @@
   "label.settings": "Settings",
   "label.share-url": "Share URL",
   "label.single-day": "Single day",
+  "label.theme": "Theme",
   "label.this-month": "This month",
   "label.this-week": "This week",
   "label.this-year": "This year",