fix end-of-document marker for multi documents return.

Add replace_if_exists as a stock method of a space.

Patch lua-yaml emitter to add \n after ---.

Still some issues with Lua console to fix, but transfer
big/sql.test to the new data dictionary at least.

Fix a bug found in the process that when altering an index
from unique to non unique the index is not rebuilt.

Remove 'lua ' prefix from schema_erase/schema_fill classes.

Store the information about spaces in a pre-recreated
system space.

https://blueprints.launchpad.net/tarantool/+spec/space-ddl

Remove space configuration from confetti.
Use transaction and space triggers to run post-DML
actions to perform DDL changes.

Implement a Lua FFI binding to disable tests.

Temporarily disable space-loading code in tarancheck
and tarantar (this breaks them).

Mostly all tests are broken.
Memcached is disabled (non-functional).

Integrate libyaml instead of internal yaml formaters.

changelog:
* fixed i64 convertion bug
* refactored bindings to new admin .info() scheme
* moved lua plugin api to separate file
* moved lua fiber api to separate file
* slab binding refactored
* added fiber lua bindings
* rewriten admin reply handler
* proper yaml end-of-document formater
* proper server error formater
* fixed bug with leftover data on stack on exception error
* added support of i64 types to lyyaml
* removed couple of box.show_ bindings
* console client fixes to support new scheme

This push has a yet broken test's.

The new server snapshot format is identical to format of
XLOG, i.e. it contains REPLACE statements with BOX_INSERT
flags for every tuple in a space.

This allows to streamline recovery, since rows from a snapshot
can be treated the same as rows from the write ahead log (XLOG).

This is an incompatible change:
 - tarantool 1.5 won't be able to read data of tarantool 1.6
 - tarantool 1.6, without extra effort, won't be able
 to read data of tarantool 1.5 (a conversion procedure is needed).

 This change as such doesn't break replication, but further changes
are in the pipeline which will inevitably finish this matter up as well.

Why this patch is necessary
---------------------------

To create system spaces dict-v5 branch employs on_replace triggers
mechanism, fired off by txn_replace(). Thus it's vital that all changes
go into spaces using txn_replace().

What else this patch does
-------------------------

- since now XLOG and SNAP have the same format, log_io.cc
code has become a bit simpler
- struct key_def is re-factored to simplify dynamic creation/deletion
of keys
- reference counting for tuple formats is added
- a number of error messages is improved to provide part no
in a multipart key.
- space cache is split away from space.cc into a separate
module, schema.[h,cc]

Remove space.estimated_rows from Lua.

Rewrite --init-storage to dump a compiled-in blob
instead of firing off the entire save snapshot machinery.

This should simplify bootstrap in presence of system
spaces:
there's going to be no need to implement the
code which creates system, they will be created
simply by recovery from a snapshot.

Add unit tests.

Little refactoring +xlog, +snap, snapshot->snap