Add Apache License Content in index.rst
Add Apache License Content in index.rst

Add Apache License 2.0 Content which is necessary
for ./releasenotes/source/index.rst.

Change-Id: Id672d7d4beaf673e75ca81d71ab1326e37a9bc47

openstack/senlin,stackforge/senlin,openstack/senlin,stackforge/senlin,openstack/senlin