Break compatibility with pre-C++11, implement make_unique

@moebius, @lyon - if I understood you correctly, OVM and OM shall also be C++-11-and-up? If so, we can avoid some more ifdef complexity by just breaking compatibility now.
(If not, I'll revise my make_unique patch)

Let me know if you'd prefer separate PRs.

See merge request !13

update ACGCommon.cmake

See merge request !12

Windows ci

See merge request !11

This reverts commit c7a1e5cd.

This allows assigning property values even if the property type is
unknown, e.g. when iterating over mesh properties.