* rework contribution privacy
- add ProposalContribution.privacy
- remove ProposalContribution.no_refund
- anonymous contribution only if not logged in
- logged in contributions can be optionally attributed
- refunds can happen if a user has a refund address
* admin: upgrade react-easy-state (had memory leak)
* be: filter users private contributions for others
* Adjust copy to be more accurate.
* Add copy for setting refund addresses (#458)