Copyright year in manual page is outdated: update copyright year to
2021.

Closes #5309

I think that our current process is better. But if someone will want to
understand why we stick with it, it is good to have explicit cons and
pros.

There is discussion in #5910 about all inconsistencies
we see between Lua and SQL worlds and possible future
directions of SQL development and new types additions.

This RFC is current state of this discussion.

Part of #5910

Co-authored-by: Igor Munkin <imun@tarantool.org>
Co-authored-by: Peter Gulutzan <pgulutzan@ocelot.ca>
Co-authored-by: Mergen Imeev <imeevma@tarantool.org>
Co-authored-by: Sergey Ostanevich <sergos@tarantool.org>

Resolves #5857

Reviewed-by: Igor Munkin <imun@tarantool.org>
Signed-off-by: Igor Munkin <imun@tarantool.org>

See https://github.com/tarantool/tarantool/discussions/5634

Part of #5442

Reviewed-by: Sergey Ostanevich <sergos@tarantool.org>
Reviewed-by: Igor Munkin <imun@tarantool.org>
Signed-off-by: Igor Munkin <imun@tarantool.org>

Part of #5187

Part of #1148

As per request by Kostja, commit an RFC document with a brief history of
the vinyl metadata log infrastructure, issues it was intended to solve,
problems we are facing now, and possible ways to solve them.

Part of #4182

Part of #3271

Add description of possible redesigning of vector clocks.

This is a draft paper covering following topics:
1. Draft protocol for discovering and maintaining network topology
in case of large arbitrary network.
2. List of required changes to support this feature.
3. Open questions and alternatives.

Changes in V2:
Based or Vlad's review
1. Rewrite couple sections to make it more clear.
2. Clarify with more details and add examples.
3. Fixed error.

RFC for #3294

Part of #3328

Introducing a formal, trackable process for server enhancement.

Before working on a complex feature, please write an RFC document,
describing what and how you see changed, and get it approved.

All historical RFCs are kept in doc/rfc.

* update tarantool man page
* cross-reference tarantool and tarantoolctl pages

Moved to tarantool/doc repository.

* doc: moved to http://github.com/tarantool/doc

Fixed Lua code block formatting in box_index.rst