Allow peer to have 128 msg types

We were resticting the types to 3 bits and the 4th to indicate
it was a peer message. Instead, use the whole uint8_t and use
the top bit to indicate a peer msg.

With this, both router and e2e can have 128 msg types.
Begin implementing e2e protocol

Handle e2e connect_request, accept, connect.
Factor out peer accept, connect
Move goto labels to column 5 so we can more easily find functions
Move e2e protocol structs to a separate header
Add shutdown_rconn (routed connection)