xF2 Add-on [Wutime] Snow storm effect 1.2.1

• Fixed: Snow not working
• Added: Defer JavaScript
• Removed minified javascript for now because it seems to gimp the snow.js effect (not sure if it's a new chrome browser issue or not)

• Added: User preference setting
• Added: Ignore snow effects globally based on user preference
• User preference database setting on install/upgrade
• Removem preference on install