Ability to limit die sizes and recursion

[darkliquid]

At the moment, there is zero protection against silly die sizes or infinite recursion. This means you can roll a 1d1!, which will explode forever, or do silly sided dice like d100000000000000000000000 which, while nice to support, would be nicer if you could restrict it.

It'd also be nice to restrict the total number of dice rolled in complex rolls that make use of multiple dice, or exploding rolls.