Windmill.proto changes. Adding cumulative flag to Counter.
Windmill.proto changes. Adding cumulative flag to Counter.

Also making computation-definition fields in ReportStatsRequest optional as it is now used to report global counters as well.
----Release Notes----
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=98152613

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