core,webadmin: Remove of storage pool type

This patch removes the storage type of a storage pool, instead a storage
pool can be marked as local - contains local on host storage or shared -
contains shared storages of various types.

Bug-Url: https://bugzilla.redhat.com/1038053
Signed-off-by: Tal Nisan <tnisan@redhat.com>
Change-Id: If29a4ecb9aa284b57e9f5218ca50cf4287452e3e