Add syntax for logical operations

[RunDevelopment]

This adds syntax for logical operations in Navi. So the following code is now valid:

if a < b and b < c {
    error("Wow. Somethign went wrong!");
else {
    let value = if not cond { 5 } else { 6 };
    SomeType { value: value }
}

This should simplify a lot of code since we finally won't have to write bool::and(a < b, b < c) anymore.