Rationalize errors

Communications

Debugging code

Re-read all the code

PromoteToParent needs to be looked at: does it have to manipulate more fields?

fix up defs; add more functions

make it extendible

reduce writes (VM changed bits not available)

Delete and contract (YggFileImpl)

New segments (build root data)

DestroyDID

overflow pages for ExtendibleHash

Remove object

SnapLink without locking "to" object

needs code for ReadAheadPages, UsePages, ShareVMPageSet, ReleaseVMPageSet, ForceOutVMPageSet, ForceOutFile, ForceOutEverything, InitializeFilePageMgr, and RestoreCacheToCleanState (if they are used!)