ov paired permutations

[edeprince3]

in ccsdt, paired ov permutations can arise. three of these are recognized by the equation generation machinery:

PP2(i,a,j,b) R(ijk, abc) = R(ijk, abc) + R(jik, bac)
PP3(i,a,j,b,k,c) R(ijk, abc) = R(ijk, abc) + R(jik, bac) + R(kji, cba)
PP6(I,a,j,b,k,c) R(ijk, abc) = R(ijk, abc) + R(jik, bac) + 4 other terms

code generators need to support these permutations, too.