Update changelog for recent changes.
Adds CDTConflictResolver protocol
Adds TD_Database+Conflicts to return documents with multiple current revisions

Adds CDTDatastore+Conflicts
* wraps TD_Database+Conflicts -getConflictedDocumentIds
* moves conflictsForDocument from CDTDatastore to here
* implements enumerateConflictsUsingBlock

Adds DatastoreConflicts tests

Moves -getRevPrefix: from DatastoreCrud to CloudantSyncTests

There's a bit of code commented out in this commit as it's not quite ready. There
are some changes to TD_Database+Insertion that I want to do incrementally but don't
want to deal with the removing this code for later.
Removes some unused code and fixes a re-declaration of the 'winningRev'
object within the block. All tests pass this change in my local copy.
Breaks out a putRevision method to be used within a database transaction.

Adds TD_Database+Insertion -putRevision: winningRev: prevRevisionID: allowConflict
status: database:
This also fixes a bug regarding the winningRev pointer. Previously, winningRev
was always nil. This never seemed to affect database behavior because winningRev
is only used for notification purposes. This fix seems to be what the original
author indented and also seems to match the functionality of current CBL code.

Adds a few checks in DatastoreCrud for nil content of a CDTDocumentRevision object,
which was useful when finding bugs while breaking out -putRevision:..database
Fixes inTransaction so that it behaves as intended. rollback was set to
YES when the TDStatus was not an error.