Issue #363: Add new rest api function - getStoragePoolVolume

This patch adds new api AJAX method to retrieve specific storage pool
volume information. This method is used in template edit window.

Signed-off-by: Rodrigo Trujillo <rodrigo.trujillo@linux.vnet.ibm.com>
Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
Issue #363: Fix data/information consistence in edit template window

This patch changes edit template window to fix consistence:
- Show storagepool + volume name correctly in storagepool field after
  saving
- Show disk size according to storagepool or storagepool/volume selected
- Block disk size input box when disk is type volume (iscsi/scsi volumes
  cannot be changed)
- When changing between storagepools, shows original saved size, default
  disk size (10 GB) or the volume size

Signed-off-by: Rodrigo Trujillo <rodrigo.trujillo@linux.vnet.ibm.com>
Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>