Support multi-part keys. Allow key duplicate
compaction. Reduce storage cost, encode metadata,
do not store msgpack (except value part).
Reconstruct tuple on read using index schema.

[replication]

JOIN support temporary put to not working
condition: there is no way to access possibly
deleted space schema during the operation
for a tuple reconstruction
(multi-thread).

recreate space key_def during join; enable join

sophia: make every operation asynchronous

sophia: fix join cursor and tests

sophia: implement delayed update operation

sophia: make delete write-only

implement Handler::executeReplace

sophia: merge fixes

make upsert operation an engine specific

sophia: make update logic common to memtx

sophia-integration: switch to Sophia v1.2.3; implement upsert

sophia: add half_commit mode support

This mode disables conflict resolution for
'prepared' transactions and solves the issue with
concurrent write-write conflicts during wal write/yield.

sophia: do not allocate tuple during replace or update; refactoring

sophia: extend and reorganize test suite

sophia: implement box.sophia()

sophia: #681: support or produce error on space::alter

sophia: extend recover tests

sophia: add separate iterator tests

box: enable per-engine select

    * add executeSelect() into engine handler API
    * add MemtxIndex; move preallocated m_position from Index to MemtxIndex
    * remove it->close()
    * remove IteratorGuard class

    note: Sysview and Sophia engines yet share the same select code in
    engine::executeSelect() (which does iterator alloc-free)

box: remove close call from box_iterator_free()

Major changes:

 - All common logic and code from all serializes replaced by
   luaL_field/luaL_serializer functions
 - All features and methods were unified
 - cdata support added to JSON
 - ffi's .NULL added to JSON
 - .cfg{} method added to MsgPack, YAML and JSON
 - .new() method added to MsgPack and YAML
 - NaN and Inf checks ported from JSON
 - array vs map detection logic ported from JSON
 - support for __serialize hint added for table/cdata/userdata
 - _serializer_compact and _serializer_type superseded by __serialize
 - 64-bit integers encoding/decoding fixed in JSON and YAML
 - floating point encoding/decoding fixed in YAML
 - JSON was converted from submodule
 - New TAP-based tests added for MsgPack, MsgPackFFI, YAML, JSON

move module related tests from test/box/ to test/module/.

use new connector as client driver

This commit completely changes the data format used by Tarantool.
A new binary serialization format called MsgPack (http://msgpack.org)
has been introduced to store tuples, keys, request members, etc.
MsgPack supports various data types and hierarchical structures. Since
tuple & keys format has been changed, the binary protocol is no more
compatible with 1.5 clients.

The list of major changes:

 * Add MsgPack library and unit tests as a submodule
 * Add Lua bindings for the library and unit tests for it
 * Update IPROTO to use MsgPack for all kinds of requests
 * Change struct tuple to use MsgPack Array instead of BER-encoded fields
 * Remove fixed offsets from tuples (cannot be supported by MsgPack)
 * Replace const char *key, key_part pairs with MsgPack Arrays
 * Rework comparators and indicies to support MsgPack'ed fields
 * Merge NUM and NUM64 types into the one single type (NUM)
 * Rewrite box_lua.cc functions to support MsgPack instead of BER
 * Rewrite tuple_update to support MsgPack instead of BER
 * Totaly remove varint32 functions from all modules
 * Rework lua_tofield and YAML encoder to properly support Lua tables
 * Modifie bootstrap files and system spaces to use the new format
 * Add MsgPack support to the test system via msgpack-python
 * Update tests to use proper data types and remove unneeded box.packs

Tarantool 1.6 is the world's first MsgPack-based database!

Add first support of python backend for TT. Still need to add support of error code (now it return 0 everytime)

Reference commit  4bc5e917c8cd5fc2f6b217512ef530007529322f
(2.1.0 tag, stable).