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
typedef enum { MAP_V0, MAP_V1, MAP_V2,} mapv_t; // or something

mapv_t version;

if (assume_v0) {
     version = MAP_V0;
...

I believe is more convenient and visual handy..