Blocking token owners

[cxkoda]

The current implementation of the operator filtering logic allows token owners (also real users) to be blocked indefinitely from moving their tokens. See also #4 for a failing test.

Was this intentional? If so, what was the reasoning for it?
Even though it is the contract owners decision in the end to leave this in, I think this should not be allowed in the reference implementation.

[cxkoda]

It was stated that new collections will be required to implement the proposed operator filtering if creators want to receive any royalties from OS.
Does this mean that developers have to implement it like in the reference example? So including the ability to lock out token owner?

[operatorfilterer]

Fixed with your PR #4 - thanks!

We only check that the mandatory list of operators are blocked from transferring - implementation does not matter.