keep subscriptions up to date when accessories are replaced

[ccutrer]

but the connection is not torn down

also add the ability to modify accessories in a batch without having to regenerate all AIDs and IIDs (and other temporary data structures) at each intermediate step. You must use this mechanism if you plan on replacing an existing accessory with an equivalent one, but want to keep subscriptions intact.

[ccutrer]

ping @yfre : I believe I've addressed all of your comments

[yfre]

ping @yfre : I believe I've addressed all of your comments

@ccutrer thank you for the ping. Missed your last commit. :( Thank for the changes, it looks for me now