txn_rollback started to yield recently. Since it was invoked via a ffi
call, which must never yield, all sorts of bad things started to happen.

Ensure that every box operation can take tuple as key/tupl/operation in
both engines

Implement space:count() as a counterpart to space:len() for consistency
with space.index.

Make more abstract version of key_opts parser to re-use code
for space options.

* Extract Lua initialization code to box/lua/init.c
* Move lbox_update/upsert/delete to box/lua/index.c
* Move all legacy and buggy code to box/lua/misc.cc

No semantical code changes.

Note: lbox_select() still doesn't support EXTERNAL_UNWIND!

*)fixed gh-1070: upsert: use default tuple as the key
*)restored lost upsert tests

Added lots of checks and nice error messages.
Added lots of tests

Disallow upsert in presence of a unique secondary key.

Update tests.
Fix typos.

This regression introducing during replacing port_ffi with port_buf
by 2fcce449

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

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()

Introduce a layer of wrappers for a number of internal box functions,
dealing with accss to spaces and indexes.

These wrappers:
    * don't throw exceptions
    * have a common prefix box_
    * are exported in the server development headers

Rewrite Lua C bindings to use the public API described above.
Rewrite Lua FFI bindings to do the same.
Add test.

* style fixes
* fix a bug in key opts decoder (alter.cc)
* ensure dimension is visible in box.space
* rebuild bootstrap.snap to use the new format

*) refactoring of update operation
*) added tests

port_buf has similar purpose but uses mempool instead of realloc()

Implement basic support for stored functions in C/C++.

- split away struct func from struct func_def (function
object and function definition object).
- extend box.schema.func.create() to accept 'language' argument.
- move module API related cmake magic to its own file
- add test/lib to gitignore
- update to the new test-run
- add a test

A part of #863

A part of #863

A part of #863

Implement box.once().

Right now there is a race in box.once(), this is somethign we'll
need to fix when we have master election on simultaneous bootstrap.

The patch merely "establishes" the syntax which is going to work
most of the time.

Prerequisite for #817. Other changes:

 - Add IteratorGuard structure to call iterator_close().

Required for #194