add index hint support for operations that read indexes

SERVER-22743 Provide fast (estimated) count command

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• Closed

SERVER-7579 QueryOptimizer not choosing the right key when querying.

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• Closed

SERVER-1599 support ability to pass hint to update

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• Closed

SERVER-27848 Add index hint to aggregation and non-materialized views

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• Closed

SERVER-7568 Aggregation framework favors non-blocking sorts

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• Closed