Add a baristas only leaderboard which also tracks free swipes

[albe2669]

As of writing there are 3 different leaderboards, monthly, semester and all time. I propose adding a fourth that only the baristas can see that tracks ALL swipes. So the normal paid swipes, free filter coffee swipes, free voucher swipes and free board swipes. This way, baristas can't "hide" their real coffee addiction. Also, it's kind of fun to see the actual usage internally, even from the board.

As I proposed this, there have been a few discussions of note:

• @duckth has an SQL query that should be pretty plug and play if translated into LINQ.
• Mikkel suggested that the barista with the most coffee drunk should be forced to run GA.

There will be a few implementation difficulties:

• The leaderboards use a statistics table that is separate from the swipes. Therefore, this change would require using a different "method" for calculating the statistics than usual.
• The app would have to check whether the user is a barista when determining whether to show this leaderboard. Again, this increases the leaderboard component complexity slightly.

[albe2669]

I may add that this issue exists entirely to keep track of avborup