Fixed open issues on corrupt or inconsistent differencing disks to properly return error status.

Fixed error paths to report errors when copying a differencing disk.
Fixed structure alignment issues to produce dynamic VHDs which are compatible with Windows 7's disk management.
Fixed performance optimization which attempted to optimize dynamic disk BAT updates as dynamic disks grew.
Added -O attach option for to override consistency checks for differencing disks which may have unexpected parent GUID or timestamp values.