core: Standardize Network naming convention

The patch standardize Network naming convention.

In addition, it renames the storage_pool_id property
to dataCenterId (and its getter/setter methods).

Change-Id: I4a4b2cbda5ae5cdb5c96231d3158d3388c2abe20
Signed-off-by: Moti Asayag <masayag@redhat.com>