Finish porting index API to objective C.
Change all methods to become objective C methods.
Implement a family of virtual constructors and destructors.
Change iterator allocation scheme.

tnt_stream_reqid()

Use the index iterator API in memcached.m,
instead of hard-coded access to index internals,
which broke index abstraction.

This (temporarily) can (somewhat) break expire
in presense of SELECT command against memcached namespace,
since SELECT uses the same iterator.

Hopefully, it's only temporary, since we'll soon
be able to have more than one independent generic iterator
over the same index.

Do not pre-allocate Index object.

Fix valgrind errors.

A pre-requisite patch for turning Index into an Object:

Extract key description into an own structure, struct key.

Introduce key_config function, which
transfers configuration from confetti structure
into struct key.

This allows to decouple index construction from
key construction -- something you need
if you want a virtual constructor for index.

SHOW INFO now prints path to config
Review Dmitry's patch, fix tests.

line (if given) 2. current directory 3. INSTALL_PREFIX/etc/tarantool.cfg

Remove an accidentally committed .reject file.
Prevent this from happening again.

connector/c: unbuffered io support fix, propper error message

Port first two patches of branch index-2objc.

We decided to use objects for indexes to ease addition
of more specialized index types (such as primary key tree
indexes, spatial indexes).

Work done by Konstantin Shulgin.

Incorporates review fixes. This patch:

 - makes struct index an Objective C class,
 - adds init and free methods,
 - moves allocation of sp_tree struction to heap (used
 to be allocated in the pool allocator) since we may
 in future create/drop indexes on the fly,
 - updates method calling signatures.

paramaters use floating point representation.