Update mans, docs.

A lot of resources still need to be updated (build scripts, etc).

Needed for server/pg_type.h header

 * Install *.lua modules into ${DATADIR}/tarantool/1.5
    and *.so modules into ${LIBDIR}/tarantool/1.5
 * Fix default package.path and package.cpath
 * Install Lua headers to ${INCLUDE_DIR}/tarantool/1.5
 * Install config.h to ${INCLUDE_DIR}/tarantool/1.5
 * Add a new package - tarantool-dev (server development headers)
 * Use RPM Macroses in rpm.spec
 * Fix tarball generation for Debian
 * Use GNUInstallDirs.cmake to setup directories

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