Make commands objects instead of functions calling each other.
Now there is '?' command that can display command list and help about
individual command. Also the command handling is more distributed into
places where it belongs.
If multi-threaded dumping was enabled, then a race was possible, where
code rendered next frame while previous frame hadn't yet been dumped.
This caused previous frame data to become corrupted, leading to encode
desyncing, complete with massive artifacts.
