Allow users to make donations anonymous, or hide amount of donation

Issue Summary

Sometimes, donors on sites I maintain do not want to make it publicly visible how much they have donated, and sometimes wish their donation to be anonymous.

There are all sorts of reasons someone might do this

- modesty
- to avoid comparisons of donation sizes between themselves and others
- to avoid having people see that they donate to charity or can make large donations, for fear that people will hassle them for money
- many other reasons

I frequently have users who make donations request anonymity.

I think this should at least be an option.