Lists support last_update field.

It will be basically useful for lists that display data which is based
on some background computation and is not always fresh.

The first usage of the new concept is the list of proposals for
organization memebers. It shows when the job that marks accepted
proposals was run for the last time.

Change-Id: I840daad6c28dc3e6e92f57ccad14e8d6852a12ed
3 files changed