Merging OpenVDB exporter

[Wesley Spacebar]

I'm implementing an exporter for https://www.openvdb.org/
https://github.com/Wesxdz/SPlisHSPlasH/tree/openvdb

There are a few decisions related to the CMake build, particularly whether OpenVBD can be included as a submodule, included directly, or expected to be found on the system. OpenVDB 8.2 uses C++ 14 by default, which would require updating the Common build standard to support this syntax in the exporter code.

I am seeking feedback on these questions, as well as if there are any desired versions to use here.
Happy 2023 all, hoping the new year is filled with water sims.