Allows the initiator to use a variety of IQNs rather than just the
system IQN when creating iSCSI pools.
* docs/schemas/storagepool.rng: extends the syntax with <iqn name="..."/>
* src/conf/storage_conf.[ch]: read and stores the iqn name
* src/storage/storage_backend_iscsi.[ch]: implement the IQN selection
when detected
* src/conf/storage_conf.c src/conf/storage_conf.h: extend the enums
and values
* docs/schemas/storagepool.rng: add to the list of storage pool type
formats
- mpath pools weren't listed
- scsi pools were missing an adapter section
- iscsi pools were missing an auth section
- Logical pools do not require a source name to be specified
