Constraints for numeric unboxed types

[dahlia]

E.g.:

@numeric-constraints(min=1, max=12)
unboxed month (int32);

Possible options:

• [x] min (inclusive; cannot be used with greater-than): #271
• [x] max (inclusive; cannot be used with less-than): #271
• [ ] greater-than (exclusive; cannot be used with min)
• [ ] less-than (exclusive; cannot be used with max)