Replaced murk with Cacophony; rewrote all serialization.

dep: removed murk.
premake: imported Cacophony, removed murk-import.
README: updated dependencies list.

serialization: imported Cacophony stuff.
Object, Metadata: unified some prop error handling.

Cmd::StageImpl: reworked definition macros.
Cmd::Node::Create: stubbed out some staged.