Add function application operator §

Because $ is not a legal operator in Swift and it kinda looks the same. :grin:
2 things:

- Did this number come from Haskell's precedences?  It's a bit too low compared to everything else in the Swift STL (about 90-150).  Maybe 100 or 110 would be better.  Then again, we haven't quite gotten around to giving any of these things relative precedences yet.

- This operator associates to the right.