hey,

so we're reorganising libbitcoin into submodules like blockchain,
server, node, ...

there's a 'bitcoin' submodule which is the current main code in libbitcoin.

Would it make sense to rename this to core? or system?
So instead of:

#include <bitcoin/bitcoin.hpp>

We have either of:

#include <bitcoin/core.hpp>
#include <bitcoin/system.hpp>

I kinda like system for what it implies.