Reset IndexedDB when resetting the app

assets/javascripts/app/app.coffee

@@ -110,6 +110,7 @@
   reset: ->
     @store.clear()
     @settings.reset()
+    @db.reset()
     @appCache?.update()
     window.location = '/'
     return

assets/javascripts/app/db.coffee

@@ -108,6 +108,9 @@ class app.DB
 
     txn
 
+  reset: ->
+    try indexedDB?.deleteDatabase(NAME) catch
+
   useIndexedDB: ->
     !app.isSingleDoc() and !!window.indexedDB