[Tagging] Better term for unisex

[martianfreeloader]

In the discussion of the Gender proposal, I noted that I find it strange 
to use the term "unisex" for "gender-neutral" or "all-gender" (as sex 
and gender are different properties).

Proposal: https://wiki.openstreetmap.org/wiki/Proposed_features/Gender

My suggestion was to use gender=mixed instead of gender=unisex. However, 
the question was raised whether the meaning of gender=mixed is still 
easily understood if the feature can only be used by one person at the 
time. I think the answer is yes. But if people disagree, it would be 
great if they raise their concerns before voting starts.

Any comments?