Cleared share list status - Added confirmation box when setting list to shared

There were 850 of you guys who set your list public (in-game).
Pretty sure most of you thought it was Steam's public settings - So I've changed the terminology to 'Shared In-Game' and the public list is now 'Shared Lists'.

If you want to re-share your list, you'll have to set it again.
- NOTE - If you share your list, everyone who plays Game Quest will be able to play your list and compete in your list's leaderboard