Ewalds speed up

[ahyork]

increased speed of ewalds sum by moving kvec.wt multiplication outside of framework atom loop in the _ϕ function.

[SimonEnsemble]

v nice trick for speed up!

[coveralls]

Pull Request Test Coverage Report for Build 186

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.337%

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Totals
Change from base Build 179:	0.0%
Covered Lines:	738
Relevant Lines:	845

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💛 - Coveralls