CSHARP-601 Linq to Aggregation Framework

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• Closed

SERVER-5782 need a $literal operator to help prevent injection attacks

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• Closed

SERVER-9444 Use new Sorter for Aggregation $sort and $group

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• Closed

SERVER-9840 Add variables, $$ROOT and $$CURRENT to aggregation and make $let to set them

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• Closed

SERVER-9841 $map expression to run a sub expression on every member of an array.

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• Closed