GitLab

Merged the other-tags branch into the trunk (this wasn't an rX:Y merge, since the branch wasn't branched directly from the head of the trunk)

Moved all the includes to a subfolder yaml-cpp so they don't interfere with other libraries' includes

Converted indexing to std::size_t, and fixed the Node templated overloads to properly index any index type (determining what is an index type is a bit of a hack - it should be is_convertible<T, std::size_t> (I think), but I just explicitly wrote down a list)