Feature: Implement new validators

[syphax-bouazzouni]

Context

See agroportal/project-management#393

Changes

• Add symmetric validator (810771a)

p is symmetric enforce: A p B -> B p A

• Add distinct_of validator (05bb6cb)

p1 distinct_of p2 enforce: A p1 B ^ A p2 C -> B <> C

• Add superior_equla_to validator (5cd980d)

p1 superior_equla_to p2 enforce: A p1 B ^ A p2 C -> C <= B

• Add inverse_of validator (9ea0be8)

p1 inverse_of p2 enforce: A p1 B  -> B p2 A