(cmake): Upgrade std flag to --std=c++17

[ladislas]

Même changement que 863604b mais remis dans develop pour qu'on puisse en profiter tout de suite.

on pourra drop le commit dans #140 avant de merge dans develop.

[codeclimate]

Code Climate has analyzed commit 98d848b and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 100.0% (0.0% change).

View more on Code Climate.

[codecov]

Codecov Report

Merging #194 (98d848b) into develop (0ab9eff) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           develop      #194   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        15           
  Lines          213       213           
=========================================
  Hits           213       213           

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