Experimental sync to peers on localnetwork

[Jason Gerard DeRose]

This is an experimental feature to do automatic CouchDB replication to peers in the same Dmedia library.

First of all, this feature provides NO PRIVACY WHATSOEVER. It's secure in that non-authorized devices should not be able to write updates into your CouchDB, but it's totally insecure in that the replication is all in clear-text and non-authorized devices can capture the entire contents of your CouchDB.

Because of this, the feature is disabled by default and is deliberately difficult to enable. To peer your machines, start on one machine by running the new `init-library` script in the Dmedia source tree, like this:

jderose@jgd-ws:~/bzr/dmedia/peer-sync$ ./init-library
{
    "library_id": "YSZE4SDLZHLFB44DOCTAM5SP",
    "tokens": {
        "consumer_key": "Z3SDMP3QKLLZ7RZ5J6JWD6M6",
        "consumer_secret": "6XDZAC7D4HZIZRX47VJKMD5G",
        "token": "QGLHD4TWMXAWL2HDPASNYB6M",
        "token_secret": "DS7AK6MRYOM7BAQYNRJ3UVRL"
    }
}

The above JSON gets written to ~/.local/share/dmedia/library.json file. To then add another machine, copy the above JSON and save it as ~/.local/share/dmedia/library.json on each additional machine.

In other words, each time you run init-library, all the values are random... but to have multiple machines in the same library, you have to copy the exact same library.json file around between them.