added a way to reset client cursor batch on exception #1025
handled RetryWithWriteLock on migrate bulk clone #1025
changed DBClientCursor::BatchResetter to reset to a specific position #1025
added SpillableVectorIterator::BatchResetter #1025
added RetryWithWriteLock handling to transferMods #1025
changed handling of spilled ops in write lock #1025

Avoids holding the lock during a network call.
added test for #1025
Merge pull request #1026 from Tokutek/migrate-multikey

ensure chunk migrations can handle RetryWithWriteLock

fixes #1025