cleaned up indexing and target list changes

[jchate6]

This is what I've been working with for speeding things up.

This speeds up the target list page by ONLY plotting the points shown in the table. and indexing everything by creation date.
This also speeds up the home page search for recent targets.

It's still pretty experimental, especially with the interactions between non-superuser permissions and a large DB.

One known issue is that permissions have to be checked for each target against the user permissions.

The largest DB we know about has tens of millions of targets.