Type operator associativity

[LefterisJP]

Many of the type operators should have the associative property.

As an example the sum type:
string | i32 is the same as i32 | string and yet the current implementation does not view it as such.

I suppose same goes for product types:

string, i32, bool should be equal or at least convertible (with a warning since memory layout changes?) to any other permutation like: i32, bool, string.