Remove hashbangs.

These modules should be imported, not executed.
Add XXX about logging context.
Add config option listen_addr.
Change credential_id from int to string.

Too hard to manufacture unique integers on the frontends
in a distributed fashion.
_calculate_cred_hash: avoid special delimiter character

Length-encode all the elements of T1 instead of concatenate with
a special delimiter character to avoid abuse/misuse of the delimiter.