This is a terrible kluge, but time doesn't permit modifying the
system. All of this also touches old code that is untested, which is
difficult to modify with confidence.
* src/server/DocumentServer.js (DocumentServer#create): Use
StagingBucket.
* src/server/Server.js: Remove logic now handled by DataProcessor.
* src/server/request/DataProcessor.js (processDiff): Wrap in
StagingBucket to filter out values that do not result in changes.
* test/server/request/DataProcessorTest.js: Update failing cases.
What a cluster.
This was a lot of work to work around existing, bad APIs; there is no
time to refactor at the moment; this already took much longer than
expected.