Unmaintained Check for similar thread before posting a new one 1.0

Features:
- indicated if you already subscribed to one or more similar threads
- hover over the title and it gives a little preview of the thread's content
- no edits whatsoever needed, just import the product file, enable the Add-on and it works (well, it should )
- you can turn it off for certain forums or
- you can turn it off completely without leaving any code that messes your templates/files
- it can be translated
- don't it anymore? Remove the product and you'll never see that Add-on again