Add Gap Analysis of Capacity Management Story
Add Gap Analysis of Capacity Management Story

This patch adds gap analysis of capacity management story with the
gap-analysis-template.rst template. This patch also adds 'gap-analysis'
directory for storing gap analysis documents.

Change-Id: Ieac223b2ed6e10a8eb0352a9be8f54a79e94d933

openstack/openstack-user-stories