Fix #ajax preset link issues

After some further testing when adding new fields to entities and views, we found there are issues with the #ajax code we're using to dynamically change the "Manage selected preset" link.

The attached patch does the following:

1. Sets the default preset to the first preset in the list if none have been selected.
2. Only adds the #ajax callback when not in Views, and not adding a new field to a node. In both of these situations it fails, and cannot even save the form. I'm assuming it has something to do with ctools and field_ui ajax being nested inside of ajax.
3. Clean up the ajax callback function to match our findings.