Conflicts:
	client/tarantool/tc_cli.c

Use common context for lua reference and for trigger state.
Wrap all calls to lua_call into a try/catch block.
Introduce LuarefGuard
Remove box_luactx, it's not adding any value now.
Implement multiple triggers. Reuse code in lua/trigger.cc.
Misc cleanups.
Rename a few files.

on_replace triggers on struct lua_trigger.
Session and space triggers use the same technology.
Code cleanup.

Miscallenous cleanups and refactoring.

Add comments to trigger.h
Implement LuarefGuard - a stack object to automatically
release a Lua reference on return or exception.

Add more context to struct trigger and get rid of specialized
objects in alter.cc.

Add optional 'destroy' to struct trigger, which is required
in space-luatriggers.

msgpuck is an external project and hosts its headers within
the same directory which contains its C files.

Therefore, for msgpuck, we have to add src/lib to the header search path,
whether we want it or not.

Since it's there anyway, kill include/lib and move all
headers of all other stand-alone libraries to their respective
directories in lib/.

include_directories(src/) is a total blasphemy, and is thus
removed.

Make assoc.c a C file, not C++.

Remove dead code in recovery.c, read_log().

Factor out utility functions from lua/init.cc to lua/utils.c,
and use lua/utils.c in the rest of the code. The purpose
of lua/init.c is to initialize Lua subsystem in the server.

Decopule say.cc from the rest of the server, move to say.c

Decouple fiber.cc from tarantool_cfg.

Decouple opts.c from tarantool_cfg.

Introduce lbox_call() which wraps Lua errors into a Tarantool
exception and use it everywhere where we used to use lua_call().

Remove box/box_lua.cc:root_L, which was just a copy of tarantool_L.

Move plugin API implementation from lua/init.cc to src/plugin.c,
plugins must be available for JS and others too.

Remove unnecessary GNUisms from plugin.c (argh!)

Remove dead code which was trying to sandbox 'ffi' package.

Fix lbox_print() which prints to the log to look more like
normal print. We should implement say() bindings in the future,
for now make what we have work the way it should work.

Update ER_PROC_LUA error message text and remove noise from it
(imporves readability of Lua errors a bit).

Conflicts:
	src/box/bitset_index.cc
	test/big/tarantool.cfg

Conflicts:
	src/box/box.cc
	test/box/configuration.test

Conflicts:
	test/box/configuration.result
	test/box/configuration.test

Conflicts:
	src/tarantool.cc
	test/box/configuration.result
	test/box/configuration.test
	test/lib/server.py