Move constructors and assignment operators should be marked as noexcept

[tsdgeos]

According to https://clang.llvm.org/extra/clang-tidy/checks/performance-noexcept-move-constructor.html

Move constructors of all the types used with STL containers, for example, need to be declared noexcept. Otherwise STL will choose copy constructors instead. The same is valid for move assignment operations.

I think this is particularly important for Variant itself that sometimes is a vector of Variant

[muflub]

This should land in the next release. Thanks for the feature request.