Lua modularization - wrap built-in modules to require()

box.ipc         => require('box.ipc')
box.fiber       => require('box.fiber')
box.session     => require('box.session')
box.errno       => require('box.errno')
box.socket      => require('box.socket')
box.digest      => require('box.digest')
box.cjson       => require('box.json'), require('cjson')
yaml            => require('box.yaml'), require('yaml')
msgpack         => require('box.msgpack')
interactive     => require('box.interactive')

Closes #139
Modularization: box.time() => box.fiber.time()
Modularization: box.ipc.channel() => box.fiber.channel()
Modularization: hide internal box methods
Modularization: box.uuid() => require('box.uuid')
Merge remote-tracking branch 'origin/master' into lua-modularization

Conflicts:
	src/lua/init.cc
	test/box/auth_access.test.lua
	test/box/bsdsocket.result
	test/box/bsdsocket.test.lua
Remove src/bootstrap.h
Modularization: box.dostring() => dostring()
Merge remote-tracking branch 'origin/master' into lua-modularization

Conflicts:
	src/box/lua/schema.lua
	test/big/lua.result
	test/box/access.result
	test/box/access.test.lua
	test/box/bad_trigger.result
	test/box/bad_trigger.test.py