Multi-repo queue display should indicate which repo PRs come from

[huonw]

e.g. atm http://huon.me:54857/queue/all has three PRs all on different repos.

    #       Priority    Head ref            Title                   Mergeable   Assignee
    2       0           apasel422:enhance   Assorted cleanup        yes         Gankro
    5       0           apasel422:clean     Assorted cleanup        yes     
    11      0           apasel422:clean     Assorted cleanup        yes     

[Gankra]

:+1:, makes sense for mega-instances like ours. May implement myself.