adderall.dsl: Implement project

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
adderall.extra.misc: Implement typeᵒ

The typeᵒ goal will project one or both of its arguments, and unify one
with the type of the other, or both their types.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>