We should be able to pass UTF-8 strings to and from plugins without
python turning them into JSON-\u escapes.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We don't, but we should, like we do for normal RPC. However, I chose
to use function annotations, rather than names-ending-in-'msat'
because it's more Pythony.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>