Donations Committee to decide on questionable donations

As part of the Ways of Working Project Plan, we have to form a plan to deal with donations/sponsorships of a questionable nature. @copton and I, at a recent meeting, decided that the best way forward was to form a standing committee which could adjudicate individual cases.

The idea is that the ED would flag specific donations as worthy of deliberation, and then the Donations Committee would meet on an ad-hoc basis to decide whether to accept or reject the donation.

The document ends with a number of specific considerations we felt would be helpful in making these decisions, but these are not definitive.

@copton and I together planned out the general shape of this approach, including the specific guidelines at the bottom. I worked alone to craft the text in this MR.