Compatible API change: take std::strings by-value if we need to store them anyways:

See merge request !90

The unittests cmake pulls a copy of gtest via FetchContent.

This can prevent multiple creation and copy of strings.

This commit introduces some code generation for repeated code.
While not a fan, I believe this to superior to preprocessor magic
that would likely confuse Doxygen, humans and IDEs alike.

revert adjacent_halfface_in_cell function to halfedge version, since the edge version does not handle all self-adjacencies correctly

OVMB default codecs saved float types with the 'd' type name used for doubles instead of 'f', in effect breaking the loading of properties stored in such float formats.

See merge request !89