lib3mf Conan package

[vijaiaeroastro]

The CMake refactoring and VCPKG recipe paves the way for lib3mf conan package. This would make lib3mf's visibility better as VCPKG and Conan are the two major package managers for C++ as of now.

This is already a work in progress.

[vijaiaeroastro]

A first version has been pushed to https://github.com/3MFConsortium/lib3mf/tree/conan