add "build receive" command

Allows completed builds to be uploaded & added to the repository.

Signed-off-by: Paul Burton <paulburton89@gmail.com>
determine recent builds from time_upload

The time_start & time_end fields aren't going to be present for many
builds & time_upload is probably more useful anyway. Short term the list
will be short, but that'll soon change :)

Signed-off-by: Paul Burton <paulburton89@gmail.com>