MINOR: hlua_fcn: add Queue class

MINOR: hlua_fcn: add Queue class

Adding a new lua class: Queue.

This class provides a generic FIFO storage mechanism that may be shared
between multiple lua contexts to easily pass data between them, as stock
Lua doesn't provide easy methods for passing data between multiple
coroutines.

New Queue object may be obtained using core.queue()
(it works like core.concat() for a concat Class)

Lua documentation was updated (including some usage examples)