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

Fixed leak when adding duplicate keys (and actually changed the behavior - now we take the first instance, not the last)

Refactored emitter operator << overloads to not template them, so it's easier to overload for pointer types

Fixed flow folding, and made the separation slightly cleaner (but the whole scanscalar thing could use a major refactoring)

(Actually) fixed the folding newline bug, but it's a bit messy, and we don't accurately make the distinction between block folding and flow folding