Fixed a pair of minor bugs:
1)Fixed multidim_test, it could occasionally crash
2)Fixed rtree_misc.test.lua, snapshot test part
3)Reverted another rtree key mode -
  ind:select{0, 0, 10, 10} and
  ind:select{{0, 0, 10, 10}} - both works now

Don't create an extra port_buf object, to process a request. Eliminate
obsolete wrappers, such as process_ro().

Call box_select() directly from iproto and Lua/C bindings,
bypassing process_rw entry point. Saves a few CPU cycles
and opens the path for further refactoring.

Remove one usage of box_process which we aim to eliminate.

* make sure long-run tests pass
* more systematic approach to downcasts to MemtxIndex in
alter/system spaces code

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()

Reason: net.box depends on src/box/lua/tuple.h, src/box/lua/schema.lua,
src/box/lua/call.cc and these dependencies impossible to fix.

box.cfg{} is not required for net.box.

reverts commit 19343e71

* struct stat_counter keeps all statistics data (supports several instances)
* test sends 100 rps, but this methods count only 80
* stat counting bug fixed
* style fixes
* renamed as stat.c to rmean.c

No semantical code chagnes.

* msgpack encoding with lua c api(call, insert, eval, ping)
* remove extra hash lookup in net.box
* review fixes for netbox-write
* rewrite all encoding fucntions using Lua/C
* replace channels with fiber.sleep()/fiber.wakeup()
* review fixes (remove an unnecessary include)

Conflicts:
	src/CMakeLists.txt
	src/ffisyms.cc
	src/lua/init.cc
	test/unit/CMakeLists.txt