Feature pithoschanges

Includes the necessary changes for better integration with Pithos

Noticeable changes:

* Add signature for v2 maps
* Add v0 map hint
* Support map creation from a given object list
* Remove "archip_" prefix from maps and blocks created by archipelago
* Add rename functionality
* Immediately delete writeable objects when removing a map
* Add readonly option when mapping a volume
please use the code tags for better indentation.
```
v0_size = pr->req->contaddr_size;

if (map->version == MAP_V0 && v0_size != UNUSED) {
    nr_objs =__calc_map_obj(v0_size, MAPPER_DEFAULT_BLOCKSIZE);
    if (map->nr_objs != nr_objs) {
        XSEGLOG2(&lc, E, "Size of v0 map invalid. "
                            "Read %llu objs vs %llu expected",
                             map->nr_objs, nr_objs);
        goto out_err;
    } else {
        map->size = v0_size;
    }
}
```

The above code snippet does not reflect my commit. Should I assume you only meant to demonstrate your previous recommendations? If so, please review my objections above.