Get rid of accumulated named resource operations

The first version of the Launchpad web service will expose many pieces of functionality as custom named operations. Code currently landed or in the works includes custom operations called "members_by_status", "people", "create_person", and "change_status". While some Launchpad functionality really is best exposed as a named operation, all the existing operations and most of the ones we'll expose in the first version of the web service can be subsumed into standard methods of our basic Entry and Collection resource classes.

This is not the place to design that subsumption, but I'll note briefly how to change our existing custom operations into standard operations. "members_by_status" is a filter on the collection of a team's members. "people" is a filter on the collection of people. "create_person" is a factory method on the collection of people. "change_status" is the modification of one of a bug task's fields (status) and can be subsumed into the existing PUT/PATCH mechanism.

Whenever I implement a named operation I will explain how to get rid of it and include an XXX that links to this bug. If I think we can't or shouldn't get rid of the operation, I'll say so. The default position should be that custom operations must justify their existence.