socket.tcp_server() changes:

 * Set nice fibers names for listener and clients
 * Use only one address for bind
 * Return single socket instead of wrapper
 * Add opts = {} to arguments
 * Automatically remove UNIX domain socket on server:close()

Other changes:

 * Fix buggy port number parsng for ipv6
 * Add peer address to accept() results like recvfrom()

Fixes compatibility with third-party modules.

This patch also adds argument checking to all socket methods.

(fix httpd log messages)

Add a testcancel() call to iowait().
A test case will be added to 1.6, where it's easier to do.

This patch fixes logic of non-blocking tcp connect as it
described in man pages and Unix Network Programming vol.1.

Update the user guide.

1) Backport `path_find`
2) Disable debuginfo in RPM
3) Disable failing part of BSDSocket test

+ fix socket:readline regexp.

+ fix bsdsocket test

 * Move source files to appropriate location
 * Remove C wrapper for isysconnect/sysbind/sendto and
 * other functions
 * Remove box.socket.errno()
 * Change sockets to be non-blocked by
 * default
 * Code style fixes
 * Other minor changes

 + memory leak in box.net.box (timeouted responses)
 + remote:ping() never throw exception

Closes #161

move module related tests from test/box/ to test/module/.

Summary:
* PLUGIN_DIR -> MODULE_DIR
* MODULE_DIR prefix is /usr/lib/tarantool/VERSION
* MODULE_DIR automatically appends to both lua c/path
* removed plugin autoload facility in src/lua/init.cc
* removed admin console plugin dependencies
* moved src/box/lua/sql.lua to separate module = require('box.net.sql')
* moved src/plugin/pg = require('box.net.pg')
* moved src/plugin/mysql = require('box.net.mysql')
* default .so and .lua install is lib/tarantool/modules/{box/net/}
* debian spec and tests are updated

Rationale:
Any error which implies a system administrator action needs to be
marked explicitly in the log, so that it's easy to find and act
upon.

This change the number of log levels, so the default log level was
bumped from 4 to 5. Installations which set the log level
explicitly need to adjust their setting.

+ use luaL_ref/luaL_unref to store lua scalar instead lua metatable.
+ add :is_closed method.

fixes, follows from discussion https://github.com/tarantool/tarantool/issues/79#issuecomment-29309533

This patch implements show index and shows memory waste of the
slab allocator.