Move some of the implementation notes lower
Move some of the implementation notes lower

The note about indices is kind of confusing for first time users.
I am moving it lower and changing a little wording to help get
users to the API faster.

Change-Id: I1206b2b73b7ebb291685c715c8c519e33d9014bf

openstack/searchlight,openstack/searchlight,openstack/searchlight