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
A better approach and proposed solution might be:

```
enum {MAP_V0, MAP_V1, MAP_V2, MAP_V3};

typedef struct ArchipelagoHeader {
uint32_t version;
uint64_t size;
uint32_t blocksize;
uint64_t epoch;
uint32_t flags;
} ArchipelagoHeader;

#include <asm/byteorder.h>

ArchipelagoHeader *archipheader = (ArchipelagoHeader *)malloc(sizeof(ArchipelagoHeader))

*archipheader =  (ArchipelagoHeader) {
.version = __cpu_to_le32(MAP_V3),
.size = __cpu_to_le64(size),
.blocksize = __cpu_to_le32(blocksize),
.epoch = __cpu_to_le64(epoch),
.flags = __cpu_to_le32(flags),
};

```