Added a large grammar test to explore performance
Moved the generation of the firstOfRemaining set outside the loop for performance
Scaled up the large grammar test to be even "harder"
Added irrelevant lookahead item elimination to LR1Generator.closure(), improving performance by up to 5x on the large grammar test
Added symbol type lookahead caching to improve LR1Generator.closure() performance by another 25% or so.
Added more comments about lookahead caching
Added a TODO