opStrategy and ordering for ArithmeticPostAgg

Fixes #510
fix
handle arithmeticEx
better comment
review comment - better way to handle it
Merge pull request #692 from metamx/handle-arithmetic-ex

Handle arithmetic exception for overlow
truncate segmentGranularity
Merge branch 'arithmetic-op-strategies' of https://github.com/metamx/druid into handle-arithmetic-ex
Revert "Merge branch 'arithmetic-op-strategies' of https://github.com/metamx/druid into handle-arithmetic-ex"

This reverts commit 5245422a62a2cccb27fef1d719c62bc2126ba5b7, reversing
changes made to fe03476c53cd3e8948368097394cfb1cd75e4e30.
Merge pull request #693 from metamx/handle-arithmetic-ex

Handle arithmetic ex - additional commit for PR #692
Add test for MessageTimeRejectionPolicy

Add test for persist for MessageTimeRejectionPolicy
Merge pull request #696 from metamx/add-test

Add test for MessageTimeRejectionPolicy
prepare for next release
[maven-release-plugin] prepare release druid-0.6.146
[maven-release-plugin] prepare for next development iteration
fix cache bug with group by query and uniques
update docs
[maven-release-plugin] prepare release druid-0.6.147
[maven-release-plugin] prepare for next development iteration
fix HLL equals when comparing sparse and dense