[WIP] operate! with add_dot

[blegat]

Trying to make this work operate!(add_dot, BigInt(), [A, A], [A, A]) where A = ones(BigInt, 2, 2) to remove the need for such hacks: https://github.com/kalmarek/PropertyT.jl/blob/master/src/sos_sdps.jl#L144-L173

cc @kalmarek