Switch CGAL to use Exact_predicates_inexact_constructions_kernel

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Currently we are using the most accurate type of Kernel, Exact_predicates_exact_constructions_kernel, however it is also the slowest.

Most third party code examples using CGAL use Exact_predicates_inexact_constructions_kernel, so it is likely noticeably faster, however when I try switching there's a few compile errors to work though. It's probably worth working through them though.

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Note that the DooSabin subdivision is left out of the Subdivide method because it fails to compile, and I suspect it might be because of the use of Exact_predicates_exact_constructions_kernel.