Search Index Improvements

- Renamed the index field prefix from "element." to "profile.".
   Given that end users may wish to query on user attributes this naming
   is more logical.

- Improve "searchable" attribute
   The "searchable" attribute now excludes content from the full text search
   index but still includes the fields in the index. This allows for explicit
   searching on a field but not having it pollute the main index.

   Example: A field with the users manager. If you were searching for the user's
   manager by name you would receive the manager and all users that report to
   them. By excludging the manager field you can prevent this, but still be able
   to query a managers reports by filtering on "profile.manager:{manager name}"