fix(kernel/diff_cnstrs): copyright msg

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(kernel/expr): adding suport for universe polymorphism, and simplify metavariable representation

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(kernel/diff_cnstrs): missing include

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>