This commit doesn't change the logic at all, it simply:
- removes `realm` from onion test vector
- cleans-up markdown formatting and indents
- fixes typos and missing parenthesis
- consistently uses `_` instead of `-` for field names
- fixes math formatting (including changes from #1169 and #1158)
These use onion encoding for simple one-way messaging: there are no error returns.
However, every onion uses route blinding *even if it doesn't need to*.
You can prove what path was used to reach you by including `path_id` in the
encrypted_data_tlv.
Note that this doesn't actually define the payload we're transporting:
that's explictly defined to be payloads in the 64-255 range.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
