Save tuple field offsets for indexed fields in the tuple.
Merge tuple validation and initialization of field maps in the tuple.
Make formats work for an incorrect tuple.
Make tuple_field() inline.

Use formats when creating tuples.
Store format id in the tuple.

Refactor space cache code, create indexes
in space_create().

Remove init_storage option.

Move struct key_def into an own header.
Rename key_def methods to follow the coding style.
Rename field_data_type to field_type.
Instead of panicking on key_def initialization
error, throw an exception.

Conflicts:
	test/replication/memcached.test
	third_party/luajit

The allocator consists of a common slab cache, region and slab
allocators.
The patch provides unit tests.

It also modifies rlist_shift to be more in line with the
rest of rlist functions.

Conflicts:
	third_party/luajit

Before introducing a stronger row handler API,
eradicate tbuf from log_io/recovery, and pass around
a pointer to row and row length instead.

Extract the remaining places which access tuple->data
directly into tuple_to_port.cc file, which will have full
access to all tuple formats and all destinations to which
a tuple may need to be converted.

In this file it'll be possible to perform a conversion
efficiently, at the same time, it will be the only place
of cross-dependency between all tuple formats and all
conversion destinations.