I've added default tuple fields check against primary index key.
Primary key can yet be updated, but an old key will be
silently used anyway (copy used from update object).

Added tests.

ps. maybe it is better to validate upsert ops on execute?

Work the same way as box.stat does.

Support access by index: box.sophia['compaction.page_size']
and by call box.sophia()

Conflicts:
	src/rmean.cc

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