Add syntax to support tuples

[Fuco1]

I've been playing with the parser a bit and ended up implementing syntax for tuples for comparison operators. I'm not sure how good the implementation is, I basically turn the single nodes into a list of nodes, so this adds some overhead of creating lists where a single value would most often exist.

It allows for somewhat nice syntax like this:

buy "Metadata/Items/Armours/BodyArmours/BodyDexInt20"

repeat {
  chaos
  show
} until (tier "Intelligence", tier "Dexterity") <= (4, 4)

My initial motivation was to allow comparing rolls for divining. There's actually a lot of recipes where you want to divine, for example: harvest swapping resistances before fracturing, divining expensive mods before fracturing etc (for divining see #52)

Since some mods have multiple stats, we need to be able to write the values for all the stats, such as (hypothetical syntax roll "mod"):

if roll "flat evasion and flat energy shield" >= (300, 80) then ...

I'm not sure how to evaluate the performance hit, to me it seems to be pretty much the same. I run a somewhat complicated recipe 100 times and it came out similar, the old version was actually slower, but that's because I was a bit unlucky on the essences :D

EDIT: I implemented the roll as well so for example this is possible (divine necrotic until perfect flat). Maybe roll is not the best word here because it is both noun and a verb so someone might think it is actually doing some action. I don't have a good idea now for a different word for it though.

buy "Metadata/Items/Armours/BodyArmours/BodyDexInt20"
with "LocalBaseEvasionRatingAndEnergyShield8___"

until roll "LocalBaseEvasionRatingAndEnergyShield" = (375, 80) do divine

For a single value you can omit the parentheses of course.