Show all fields in DBRef objects

.mongorc.js

DBRef.prototype.toString = function () {
    var r = ['"$ref": ' + tojson(this.$ref), '"$id": ' + tojson(this.$id)];
    var o = this;
    for (var p in o) {
        if (p !== '$ref' && p !== '$id' && typeof o[p] !== 'function') {
            var t = typeof o[p];
            r.push('"' + p + '": ' + 
                (t == 'object' ? 'object: {...}' : '"' + o[p] + '"'));
        }
    }
    return '{' + r.join(', ') + '}';
};