* Wireless: Optimize memory usage in StreamMessageQueue (use an array of string ropes, that we only concatenate once). Allowed to relax the throttling, making transfers that much faster.
* Persist: Add a "zstd" codec, that uses the "luajit" codec, but compressed via zstd. Since both of those are very fast, it pretty much trounces everything in terms of speed and size ;).
* Persist: Implemented a "writes_to_file" framework, much like the existing "reads_from_file" one. And use it in the zstd codec to avoid useless temporary string interning.
* Metadata: Switch to the zstd codec.
