fix(library/tactic/goal): bug in the proof builder

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(builtin/num): simplify proofs using 'by simp'

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(builtin/kernel): reorder congr1 arguments

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(library/simplifier): bug using congr1 theorem

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(builtin/tactic): more meaningful error message when skip tactic is used in a full proof

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(builtin/tactic): add simp_no_assump tactic

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(builtin/num): prove strong induction and other theorems for num

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(builtin/num): prove strong induction and other theorems for num