s/MicroDesc/Microdesc/ where it appears

See merge request !360

New proposal 359: counter galois onion

Closes #186

See merge request !359

Related to arti#1923.

Revisions to prop346 and accompanying spec tweaks

See merge request !358

Prop344: Update and Categorize Vectors; Ground in Threat Model

See merge request !355

Prop#349: Decouple validation from prop#340 packing

See merge request !262

If we specify the state machines independently from prop#340, everything ends
up cleaner.

Specify that the given parameters don't exist automatically.

Explain how to apply them to onion services.

They don't belong here; this proposal is for negotiating  _new_ features.
Migrating from existing extensions isn't specified here.

It seems cleaner to have it match router descriptors.

This is analogous to our earlier tor-spec cleanup in
0fada728.

We don't want to call these things "versions";
we've already updated the rest of torspec accordingly in !352.

Also, clarify the implications of the cases where subprotocol flags
_do_ correspond to versions.

We need to keep this in sync with the extand protocols,
so it belongs in the spec.

We aren't doing this in-protocol for tor-vpn; so apparently
it doesn't get a subprotocol.

Per prop346, subprotocol numbers are _flags_, so it's okay to use a
Relay=X flag to indicate support for this cell format.

rend-spec: add a note about replay detection

Closes #246

See merge request !349

Explain why we're doing it, and the extent to which we do
(or do not) need to be perfect.

Closes #246.

proposal 355: Add a couple of footnotes

See merge request !357

Based on discussions at !356.

A couple minor spelling/grammar corrections.

See merge request !356

Proposal 358: unify the circuit handshake extensions

See merge request !354

Before they diverge any further, let's unify the `EXT_FIELD_TYPE`s
for CREATE2 and INTRODUCE2 handshakes!

Part of #214.

tor-spec: clean-ups and a new proposal (357) related to use of KH.

Closes #191

See merge request !351

I've re-grounded the entire proposal in Tor's OG Design Doc Threat Model
language, and provide a background of this threat model as part of the
introduction, to help new folks get up to speed and better conceptualize this
proposal.

The proposal has been updated to classify all vectors into the following three
categories:
  1. Internal Covert Channels
  2. Behavior Manipulation
  3. Augmented Observation

It now also proposes that Tor's threat model be expanded to explicitly cover
these categories. These categories (and their vectors) were either explicitly
excluded, or in an ambigous status before.

Additionally, the following vectors have been added:
  - Guard Trapper Attacks
  - Relay DoS/OOM

The following examples have been added to existing vectors
  - Path restriction problems
  - .exit notation
  - Exit Policy abuse by websites+exits
  - circuit dirtyness abuse by exits
  - Dropped cells types unique to onion services

Correctly note bridgedb as retired

Closes #300

See merge request !350

Modernize and clarify subprotocol sections

See merge request !352