Merge branch '1.6' of https://github.com/tarantool/tarantool

doc/sphinx/_templates/layout.html

doc/sphinx/book/app/a_errcodes.rst

doc/sphinx/book/box/authentication.rst

doc/sphinx/book/box/box_session.rst

doc/sphinx/book/box/box_space.rst

doc/sphinx/book/box/index.rst

doc/sphinx/dev_guide/box-protocol.rst

doc/sphinx/dev_guide/building_documentation.rst

doc/sphinx/dev_guide/building_from_source.rst

doc/sphinx/reference/box_error.rst

doc/sphinx/reference/csv.rst

extra/dist/CMakeLists.txt

extra/dist/example.lua

src/box/box.cc

src/box/cluster.cc

src/box/cluster.h

src/box/lua/cfg.cc

src/box/lua/load_cfg.lua

src/box/sophia_engine.cc

src/box/sophia_engine.h