Don't index browse extracts as search terms unless needed

Don't index browse extracts as search terms unless needed

In previous releases, we didn't have any major config.metabib_field
rows which had 'browse_field = true' but 'search_field = false'.  Now
that we have one (for title browse), make sure we honor the
'search_field = false' by not creating rows in the
metabib.xxxxxx_field_entry tables.

This gets us back to where we started as far as what gets into the
search index tables, but we should consider going a step further and
*not* adding the glommed row to the search tables if we are already
adding separate rows for search+browse.

Signed-off-by: Dan Wells <dbw2@calvin.edu>