No semantical changes. Style fixes, comments.

This commit completely changes the data format used by Tarantool.
A new binary serialization format called MsgPack (http://msgpack.org)
has been introduced to store tuples, keys, request members, etc.
MsgPack supports various data types and hierarchical structures. Since
tuple & keys format has been changed, the binary protocol is no more
compatible with 1.5 clients.

The list of major changes:

 * Add MsgPack library and unit tests as a submodule
 * Add Lua bindings for the library and unit tests for it
 * Update IPROTO to use MsgPack for all kinds of requests
 * Change struct tuple to use MsgPack Array instead of BER-encoded fields
 * Remove fixed offsets from tuples (cannot be supported by MsgPack)
 * Replace const char *key, key_part pairs with MsgPack Arrays
 * Rework comparators and indicies to support MsgPack'ed fields
 * Merge NUM and NUM64 types into the one single type (NUM)
 * Rewrite box_lua.cc functions to support MsgPack instead of BER
 * Rewrite tuple_update to support MsgPack instead of BER
 * Totaly remove varint32 functions from all modules
 * Rework lua_tofield and YAML encoder to properly support Lua tables
 * Modifie bootstrap files and system spaces to use the new format
 * Add MsgPack support to the test system via msgpack-python
 * Update tests to use proper data types and remove unneeded box.packs

Tarantool 1.6 is the world's first MsgPack-based database!

An older version of xmllint failed to validate a broken
URL.

The URL led to nowhere, so this also fixes a few dangling
links.

Use olink & targetptr instead of link & linkend, as is the
convention in the rest of the manual.

Give internal links a bit longer names (as is also convention
in the rest of the manual).

Add comments, update the manual.

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).

removed dead code block

n  - big endian int16
N  - big endian int32
qQ - big endian int64
f  - float
d  - double

Incompatible change,
https://blueprints.launchpad.net/tarantool/+spec/cardinality-arity

cardinality is how many unique elements a set contains. wrong term
for the max number of fields in a tuple

Hat tip to Alexey Panfilov