Don't nest / dedup subscriptions for single-items
Don't nest / dedup subscriptions for single-items

If we've just got a single item, we don't need to create a superior
Subject, just return the single item.

Also, fix a dumb copy-pasta bug where we dedup an Invalidate but return
an Insert

shana/Akavache,christer155/Akavache,ghuntley/AkavacheSandpit,shana/Akavache,kmjonmastro/Akavache,MarcMagnin/Akavache,PureWeen/Akavache,martijn00/Akavache,bbqchickenrobot/Akavache,MathieuDSTP/MyAkavache,Loke155/Akavache,akavache/Akavache,mms-/Akavache,jcomtois/Akavache,gimsum/Akavache