more generic implementation of array_of_doubles_sketch

[AlexanderSaydakov]

array_tuple_sketch , union, intersection, a_not_b with parameterized array type and policy

[AlexanderSaydakov]

Motivation: I found that array_ofdoubles was too rigid: doubles only, no way to change update policy and union policy, and no way to substitute our custom array with std::vector In this implementation all array_ofdoubles types are just aliases with default policy (if applicable) and array, but easy to have any type like std::vector or something. I am not sure if the name arraytuple* is the best. Suggestions are welcome.

[coveralls]

Pull Request Test Coverage Report for Build 6660511473

• 92 of 92 (100.0%) changed or added relevant lines in 8 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 98.941%

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Totals
Change from base Build 6578009132:	0.0%
Covered Lines:	16070
Relevant Lines:	16242

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💛 - Coveralls

[jmalkin]

Merge away!