Add sorting of beacons in example apps

[ghost]

In examples apps that display lists of beacons and BLE devices, the list can be sorted, by RSSI, distance etc.

Sorting function from Alexis:

function sortBeaconsByProximity(beacons) {
    var beaconKeyRssiArray = [];
    var sortedBeacons = {};

    for (var key in beacons) {
        beaconKeyRssiArray.push([beacons[key], key, beacons[key].rssi]);
    }

    beaconKeyRssiArray.sort(function(a, b) {
        return b[2] - a[2];
    });

    for (var i = 0; i < beaconKeyRssiArray.length; i++) {
        sortedBeacons[beaconKeyRssiArray[i][1]] = beaconKeyRssiArray[i][0];
    }

    return sortedBeacons;
}