StoreEntry conflation : storeAppendPrintf is in the wrong place.

I think we should nuke storeAppendPrintf : its really a overloaded
concept. The Packer (which in c++ can be a stream easily) is something
that is easy to acquire /on/ an entry, and makes the various debugging
routines and stats routines we have less coupled to the store, and
rather coupled to the stream interface.

Rob

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