Overhauling of the remote connection and replication implementations

[whitfin]

Right now there's a neat little bug with remote connections (in that they don't work at all). This is just down to a bad Mnesia config and can easily be fixed.

However, I found this during a run through of various replication scenarios and realised that we don't handle node dropping very well, at all. I have no good ideas at this point of how to fix, but I'm dumping all thoughts into this issue to get them on "paper".

Ok, so things to do out of this:

• Add a Cachex.add_node/2 function to add nodes dynamically (this also helps from remote consoles)
• Add a way to update a working state, for example if a local node becomes remote
• Ensure that tables are replicated around - this will stop crashes on node drops