Bug 2267: Reuse leaf and leaf set entry builders in NormalizedNodeInputStreamReader

Builders.leafBuilder() and Builders.leafSetEntryBuilder() can be
re-used. Added class members to lazy-create a reusable an instance of each.

Also fixed a bug related to a null revision field in QName.

Change-Id: Ief41b6c23d9f41dc0d281786e5143127ef88ca4d
Signed-off-by: tpantelis <tpanteli@brocade.com>
Merge "Bug 2267: Reuse leaf and leaf set entry builders in NormalizedNodeInputStreamReader"